THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


SANITAKY  AND  APPLIED  CHEMISTET 


A  TEXT-BOOK  OF 

SANITARY  AND    APPLIED 

CHEMISTRY 

OR 

THE  CHEMISTRY  OF  WATER, 
AIR,  AND  FOOD 


BY 

E.  H.  S.  BAILEY,  PH.D. 

PROFESSOR  OF  CHEMISTRY,  UNIVERSITY  OF  KANSAS 


SECOND  EDITION 


"Neto  fforfc 
THE  MACMILLAN  COMPANY 

LONDON :  MACMILLAN  <fe  CO.,  LTD. 
1912 

All  rights  reserved 


COFTBIGHT,    19M, 

BT  THE  MACMILLAN  COMPANY. 


Set  up  and  electrotyped.     Published  July,  1906. 
Reprinted  February,  1908;  January,  1910; 
February,  xgxi;  July,  19x2. 


Xortoooti 

J.  S .  Cubing  it.  Co.  —  Berwick  &  Smith  Co. 
Norwood,  MM*.,  O.8.A. 


Lftrary 


/ 
/f/2. 

PREFACE 

THE  object  of  this  work  is  to  furnish,  a  text-book  upon 
applied  chemistry  that  is  suitable  for  use  by  those  students 
who  have  had  a  course  in  general  chemistry,  such  as  is 
usually  completed  in  a  good  high  school  or  in  the  earlier 
years  of  a  college  course.  The  particular  phase  of  applied 
chemistry  treated  is  that  which  pertains  to  the  daily  life 
of  the  household,  but  the  subjects  considered  do  not  by  any 
means  cover  the  whole  field  of  what  might  be  called  chem- 
istry applied  to  daily  life,  but  only  the  most  important 
topics. 

Although  primarily  intended  for  use  as  a  text-book,  much 
scattered  material  is  here  collected  from  Government  Re- 
ports and  elsewhere,  so  that  it  is  believed  the  book  will 
prove  valuable  for  general  information  and  reference.  The 
difficulty  of  condensing,  without  sacrificing  something  in 
clearness,  is  thoroughly  recognized. 

Some  simple  reactions  in  general  and  organic  chemistry 
have,  it  is  true,  been  introduced,  but  it  is  believed  that  they 
are  of  a  kind  to  be  readily  understood  by  students,  with  a 
little  explanation  from  the  instructor.  It  would  be  well  to 
supplement  the  text  by  lectures  on  the  topics  studied  and 
also  to  give  time  for  discussions. 

The  author  believes  that  a  practical  method  for  teaching 
the  subject,  if  a  sufficient  number  of  books  of  reference  are 
at  hand,  is  to  outline  topically  the  subject  to  be  studied  and 
require  a  preparation  on  those  topics  from  the  student. 

It  has  been  the  intention  of  the_author  to  introduce 


VI  PREFACE 

enough  facts  to  render  the  subject  intelligible  and  readily 
comprehended,  and  not  to  burden  the  pages  with  details 
which  belong  properly  to  a  more  voluminous  treatise  on 
the  subject. 

One  of  the  most  important  features  of  the  book  is  the 
introduction  of  experiments,  which  are  distributed  through- 
out the  text  and  which  it  is  believed  will  very  materially 
aid  the  instructor  who  may  have  occasion  to  direct  the  work 
of  the  students.  These  experiments  are  suggested  by  several 
years  of  experience  with  classes  in  Sanitary  and  Applied 
Chemistry,  and  they  are  of  such  a  character  as  can  be  per- 
formed in  any  chemical  laboratory  and  with  a  moderate 
amount  of  inexpensive  apparatus.  More  difficult  experi- 
ments, which  would  involve  a  knowledge  of  quantitative 
analysis,  have  been  purposely  omitted.  The  instructor  can 
add  more  experiments,  if  sufficient  apparatus  is  at  hand  and 
the  time  allotted  to  the  course  will  permit. 

The  first  part  of  the  book  is  devoted  to  water,  air,  heat- 
ing, lighting,  and  ventilation,  —  to  those  practical  problems 
with  which  we  come  in  contact  every  day ;  and  the  second 
part  is  occupied  with  a  discussion  of  foods  and  beverages. 
In  the  latter  section,  although  many  adulterants  are  pointed 
out  and  the  simpler  tests  for  them  are  given  in  the  experi- 
ments, no  attempt  is  made  to  do  the  work,  which  properly 
belongs  to  the  trained  microscopist  or  analytical  chemist. 

For  many  valuable  suggestions,  which  were  made  while 
the  book  was  going  through  the  press,  and  for  assistance  in 
reading  proof,  the  author  is  especially  indebted  to  Professor 
J.  T.  Willard,  Dr.  James  Naismith,  Professor  Isabel  Bevier, 
Professor  M.  A.  Barber,  Dr.  H.  P.  Cady,  Dr.  W.  D.  Bigelow, 
Professor  W.  C.  Hoad,  and  Mrs.  A.  T.  Bailey. 


CONTENTS 

R4tt 

INTRODUCTION xix 

PART  I 
SANITARY  CHEMISTRY 

CHAPTER  I 
THE  ATMOSPHERE 

History  —  Proof  that  air  has  weight  —  Experiments  of  Galileo, 
Torricelli,  and  Lavoisier  —  Experiments  by  Cavendish  and 
by  Bunsen,  Leroy,  and  Regnault  —  Recent  discoveries  by 
Ramsey  and  Rayleigh  —  Methods  used  for  detecting  argon 
and  helium  —  Composition  of  the  air  —  Experiments  to  illus- 
trate composition  of  air  —  Proof  that  air  is  a  mechanical 
mixture  —  Methods  used  for  analysis  of  air  —  Oxygen  in 
expired  air  —  Moisture  in  the  atmosphere  —  Proof  that  moist 
air  is  lighter  than  ordinary  air  —  Experiments  illustrating 
the  presence  of  moisture  in  air —  Carbon  dioxid  in  free  air 
and  in  closed  rooms  —  Effect  of  impure  air  upon  the  system 
—  Experiments  to  show  the  amount  of  carbon  dioxid  in  the 
air  —  Nitric  acid,  ammonia,  and  other  impurities  in  the 
atmosphere  —  Ozone  and  its  properties  —  Experiments  upon 
ozone  —  The  effect  of  carbon  monoxid  upon  the  system  — 
Substances  in  suspension  in  the  air  —  Methods  of  studying 
the  dust  of  the  atmosphere  —  Bacteria  in  city  air  —  Micro- 
organisms not  abundant  at  great  altitudes  —  Infectious 
diseases  readily  propagated  by  dust  —  Arsenic  in  the  air  — 
Experiments  to  show  presence  of  arsenic  in  papers  and 
fabrics  —  Injurious  trades  —  Composition  of  ground  air  — 
Source  of  the  impurities  in  ground  air — Effects  of  ground 
air  upon  the  system  —  Offensive  gases  .  .  .  .  1 


Vlll  CONTENTS 

CHAPTER   H 

FUELS 

MM 

Combustible  elements  in  fuels  —  How  heat  is  produced  by  com- 
bustion —  Cellulose,  the  basis  of  ordinary  fuels  —  Wood  as 
fuel  —  Amount  of  water  in  different  woods  —  Effect  of  dry- 
ing upon  wood  —  Composition  of  wood  ashes  —  Charcoal  — 
Method  of  making  charcoal  —  Peat  —  Occurrence  and  prepa- 
ration—  Coal  —  Characteristics  of  different  kinds  of  coal  — 
Composition  of  different  coals  —  The  analysis  of  coals  — 
Natural  and  artificial  gases  as  fuel — Advantages  of  gas  as 
fuel  —  Burners  used  with  gas  —  Composition  of  natural  gas  .  23 

CHAPTER  in 
HEATING  AND  VENTILATION 

Common  methods  of  heating  —  Use  and  economy  of  the  fireplace 

—  The  stove  as  a  heating  device  —  Use  of  the  hot-air  furnace 

—  Use  of  steam  with  direct  and  indirect  radiation  —  Advan- 
tages of  hot- water  heating  —  Electricity  as  a  source  of  heat 

—  Ventilation  —  Why  little  attention  is  paid  to  this  subject 

—  Necessity  for  ventilation  —  Amount  of  air  used  up  in  respi- 
ration—  Contamination  of  air  by  lights  —  Properties  of  im- 
pure air  —  Amount  of  fresh  air  necessary  to  health  —  Crowd 
poisoning  —  Conditions   necessary  for  good  ventilation  — 
Mechanical  system  of  ventilation  —  Devices  used  for  venti- 
lating ordinary  rooms  —  Experiments  upon  air  currents  and 
temperature 33 

CHAPTER  IV 
LIGHTING 

Sources  of  artificial  light — Solid,  liquid,  and  gaseous  light-pro- 
ducing substances  —  The  candle  flame  —  Experiments  with 
the  candle  flame  —  Use  of  gas  for  illuminating  purposes  — 
History  of  the  development  of  artificial  light  —  Candles  as  a 
source  of  light  —  Composition  of  candles  —  Method  of  mak- 
ing candles  —  Use  of  kerosene  for  lighting  —  Sources  of  coal 


CONTENTS  IX 

PAGI 

oil  and  method  of  making  —  Distillates  from  Pennsylvania 
petroleums  —  Adulteration  of  kerosene  —  Experiments  to 
show  the  flash  point  of  oils  —  History  of  illuminating  gas  — 
Method  of  making  gas  —  By-products  in  gas  manufacture  — 
Method  of  making  water  gas  and  its  properties  —  Preparation 
and  properties  of  air  gas  —  Pintsch  gas  —  Calcium  carbid 
and  its  use  in  making  acetylene  —  Composition  of  illuminat- 
ing gases  —  Experiments  upon  coal  gas  —  Experiments  upon 
acetylene  gas  —  Lamps  used  for  the  burning  of  oils  —  Incan- 
descent gas  lights  —  Method  of  making  mantles  and  their 
composition  —  Advantages  of  incandescent  lights  —  Electric 
lights  —  The  ideal  light  of  the  future  .  .  .  .  .46 

CHAPTER  V 

WATER 

Impurities  in  water  —  Source  of  impurities  in  water  —  Character 
of  rain,  river,  lake,  and  well  waters — Mineral  waters  —  Ex- 
periments upon  mineral  substances  in  water — Hard  waters 

—  Disadvantages  of  the  use  of  hard  water  —  Experiments 
on  hard  water  —  Organic  impurities  in  water  —  Source  of 
these  impurities  —  The  sanitary  analysis  of  a  water  —  Mean- 
ing of  the  presence  of  free  ammonia,  albuminoid  ammonia, 
nitrates,  nitrites,  and  chlorin  in  a  drinking  water — Experi- 
ments to  determine  the  quality  of  water  —  Analysis  of  city 
water  supplies — Table — Drinking  water  and  disease — Effect 
of  suspended  matter  in  water  —  Organic  impurities  in  water 

—  Illustration  from  the  city  of  Massina  —  Illustration  from 
the  Valley  of  the  Tees,  England  —  Illustration  from  Plym- 
outh,   Pennsylvania  —  Illustration    from    Hamburg,    Ger- 
many —  The  cause  of  pollution  of  ordinary  wells  ...      61 

CHAPTER  VI 
PURIFICATION  OF  WATER  SUPPLIES 

Method  of  purifications  by  sedimentation,  dilution,  and  oxidation 

—  Filtration  by  the  English  filter  bed  system  —  Mechanical 
filtration  —  Clark's  process  —  Household  filtration  —  Storing 
ground  water  —  Effect  of  freezing  upon  water       ...      79 


X  CONTENTS 

CHAPTER   VH 
SEWAGE:   DISPOSAL  OF  HOUSEHOLD  WASTE  AND  GARBAGB 

PA6B 

Composition  of  sewage  —  Oxidation  of  sewage  —  Modern  theories 
for  purification  of  sewage  —  Disposal  of  sewage  by  dilution 

—  The  sewage  of  Milwaukee  and  Chicago  —  Disposal  of 
sewage  by  irrigation  —  Intermittent  filtration  —  The  septic 
tank  —  Precipitation   of   sewage  —  Disposal   of  household 
waste  —  The  use  of  the  stove  or  furnace  for  disposal  of  waste 

—  Burying  in  the  soil  —  Methods  used  for  disposing  of  waste 
in  large  cities  —  Cremation  as  used  abroad — "Reduction" 

of  garbage  and  utilization  as  a  fertilizer         ....      84 

CHAPTER  VIII 
CLEANING:  USE  OF  SOAP  AND  BLUING 

Necessity  for  cleanliness  —  Cleaning  materials  act  mechanically 
or  chemically  —  Polishing  powder  —  Borax  —  Ammonia  — 
Cleaning  leather,  wood,  etc.  —  Solvents  for  grease  —  Cleaning 
marble  —  Use  of  solvents  upon  household  fabrics  —  Removal 
of  grease  by  blotting  paper,  French  chalk,  fuller's  earth  — 
Treatment  of  paint  spots  with  oil  and  turpentine  —  Sugar 
and  acid  spots  —  Ink  spots  —  To  clean  tarnished  silver  — 
Cleaning  polished  brass  and  copper  —  Experiment  to  remove 
iron  rust 92 

Soap :  History  of  the  discovery  of  soap  —  Raw  material  used  in 
its  manufacture  —  Process  of  saponification  —  Method  of 
making  soap  commercially  —  Mottled,  toilet,  transparent, 
and  perfumed  soaps  —  Scouring  soaps  and  their  use  —  Soft 
soap  —  No  economy  in  the  use  of  a  cheap  soap  —  Advantage 
of  a  well-dried  soap  —  Theories  in  regard  to  the  action  of 
soap  —  The  use  of  hard  water  —  Experiments  upon  making 
soap  and  in  testing  its  composition  —  Washing  soda  —  Ex- 
periments to  test  a  washing  powder 96 

Bluing :  Use  of  indigo  —  Prussian  blue  for  making  liquid  blue  — 
Ultra  marine  and  its  use  as  a  bluing  material — Experiments 
with  Prussian  blue  and  with  ultra  marine  —  Aniline  colors 
as  used  in  liquid  blues 103 


CONTENTS  XI 

CHAPTER  IX 

DISINFECTANTS,  ANTISEPTICS,  AND  DEODORANTS 

PAGE 

The  necessity  for  using  disinfectants  and  antiseptics  —  The  im- 
portance of  the  sense  of  smell  —  Tests  for  disinfectants  — 
How  bacteria  multiply  —  An  ideal  disinfectant  —  Use  of  the 
following  disinfectants  and  antiseptics:  Sunlight  —  Dry  air 

—  Dry  earth  —  Charcoal  —  Experiments  upon  the  action  of 
animal  charcoal  —  Dry  heat  and  its  use  —  Sulfur   dioxid 
as  a  disinfectant  —  Carbolic  acid  and  its  value  —  Copper  sul- 
fate  —  Iron  sulfate  —  Zinc  chlorid  —  Potassium  permanga- 
nate—  Fire  the  most  effective  means  of  destroying  disease 
germs  —  Steam  as  used  for  destruction  of  germs  —  Boiling 
water  and  how  it  may  be  used  —  Chlorid  of  lime,  its  value 
and  use  —  Formaldehyde  gas  and  the  method  of  applying  it 

—  Corrosive  sublimate  and  its  value  as  an  antiseptic    .        .     106 


PART   II 
CHEMISTRY  OF  FOOD 

CHAPTER  X 
FOOD 

Definition  of  food  —  Distinction  between  food  and  medicine  — 
Uses  of  food  —  Delicacy  of  the  sense  of  taste  —  Experience 
has  been  our  guide  in  selecting  food  —  Variety  of  food  — 
Value  of  a  mixed  diet  —  Selecting  food  suited  to  habit  and 
employment  —  Reasons  for  cooking  foods  —  Food  used  to 
build  up  the  tissues  and  supply  energy  —  Synthetic  foods  — 
Elements  contained  in  the  body  —  Amount  of  substances 
occurring  in  the  body  —  Carbohydrate  and  nitrogenous  foods 
—  The  cellulose,  cane  sugar,  and  glucose  groups  —  Proximate 
substances  contained  in  foods,  viz.  water,  fat,  carbohydrates, 
protein,  organic  acids,  and  mineral  salts  ....  117 


XU  CONTENTS 

CHAPTER  XI 
CELLULOSE,  STARCH,  DEXTRINE,  LEGUMES 

MM 

Occurrence  of  cellulose  and  its  properties  —  Experiments  upon 
cellulose  —  Sources  of  starch  and  amount  found  in  various 
cereals  —  Wheat,  its  composition  —  Comparison  of  different 
grades  of  wheat  —  The  composition  and  properties  of  wheat 
flour  —  Analysis  of  different  kinds  of  flour  —  Milling  prod- 
ucts of  flour  —  Corn  — Composition,  properties,  and  uses — 
Comparison  of  wheat  and  corn  —  Oats  —  Composition  and 
peculiar  characteristics  —  Rye  —  Its  source,  composition, 
and  use  —  Barley  —  Its  composition  —  Rice  —  Its  cultiva- 
tion, composition,  and  properties  —  Potatoes  —  History 
of  the  introduction  of  potatoes  —  Composition  and  value  of 
potatoes  —  This  tuber  not  suited  for  use  as  a  staple  article 
of  diet  —  Composition  of  sweet  potatoes  —  Cassava  (tapioca) 
—  Its  source  and  method  of  manufacture  —  The  source  and 
method  of  preparing  arrowroot  —  Properties  of  other  starches, 
sago,  tows  les  mots,  etc.  —  Adulteration  of  starch  and  method 
used  for  the  detection  of  adulteration  —  Legumes —  Cultiva- 
tion of  the  members  of  the  Pulse  Family  —  Properties  of 
the  legumes  —  Composition  of  peas,  beans,  and  lentils  — 
Experiments  upon  legumes  —  Value  of  legumes  as  a  food  — 
Bananas  —  Starch  —  Sources  of  commercial  starch  and 
method  for  making  —  Experiments  upon  starch  —  Dextrine 
and  method  of  making — Gums  —  Inulin  —  Physical  proper- 
ties of  starch  —  Experiments  with  starch  grains  —  Chem- 
ical properties  of  starch — Experiments  in  making  starch 
and  to  show  its  properties  —  Experiments  upon  dextrose  — 
Experiments  with  diastase 126 

CHAPTER  XH 
BREAD 

Primitive  method  of  making  bread  —  Two  general  methods  of 
making  dough  light  —  First,  non-fermentation  method  ;  sec- 
ond, fermentation  method  —  Bread  not  raised  with  fermen- 
tation :  by  the  use  of  eggs,  alcoholic  liquors,  ammonium 
carbonate,  baking  soda,  baking  soda  and  molasses,  carbon 


CONTENTS  X1U 

PA8« 

dioxid,  baking  soda  and  hydrochloric  acid,  baking  soda 
and  sour  milk,  baking  soda  and  cream  tartar  —  Baking 
powders  —  Cream  tartar  powders  —  Phosphate  powders  — 
Alum  powders  —  Experiments  with  baking  powders  — 
Bread  raised  by  fermentation :  first,  by  use  of  yeast ; 
second,  by  use  of  leaven ;  third,  by  the  salt-rising  process 

—  Composition  and  properties  of  yeast  —  Method  of  mak- 
ing yeast  —  Theory  of  use  of  leaven  —  What  takes  place  in 
the  salt-rising  process  —  Chemistry  of  the  fermentation  of 
dough  —  Essentials  to  be  noted  in    making  good  bread  — 
Construction  and  use  of  the   oven  —  Temperature  used  in 
baking  —  Difference    between    fresh    and    stale   bread  — 
Amount  of  bread  that  can  be  made  from  a  given  weight 
of  flour  —  Composition  of  different  kinds  of  bread  —  Dif- 
ference between  the  crumb  and  crust  —  Starch  alone  will 
not  sustain  life  —  Value  of  a  mixed  diet  to  man  —  Bread  a 
nutritious  food  —  Value  of  white  vs.  whole- wheat  bread  — 
Patent  flour  —  Stale  bread  and  why  it  is  wholesome  —  Corn 
bread  —  Why  some  bread  is  bad  —  Adulteration  of  flour  and 
bread  —  Use  of  copper  sulfate  to  make  bread  white  —  Use  of 
alum  as  an  adulterant  —  Experiments  upon  copper  sulfate  in 
bread  —  Experiments  to  detect  alum  —  Occurrence  of  ergot 

in  flour 164 

CHAPTER  XTII 
BREAKFAST  FOODS  AND  OTHER  SPECIAL  FOODS 

Breakfast  foods  and  their  composition  —  Conclusion  in  regard  to 
the  use  of  breakfast  foods  —  Foods  for  infants  and  invalids 

—  Macaroni,    vermicelli,   etc.,    as  foods — Composition  of 
macaroni 180 

CHAPTER  XTV 

SUGARS 

History  and  classification  —  Consumption  of  sugar  in  different 
countries  —  Different  sugars  known  to  the  chemist  —  Classi- 
fication of  sugars  —  The  sucrose  and  glucose  groups  — 
Members  of  the  sucrose  group  —  Sources  of  cane  sugar — 
The  sugar  cane  as  a  source  of  sugar — Cultivating  the  sugar 


XIV  CONTENTS 

cane — Extraction  of  the  juice — Purification  of  the  juice  by 
the  use  of  sulfurous  acid  —  Concentration  of  the  juice  in 
the  "triple  effect"  and  in  the  vacuum  pan  —  Use  of  the 
centrifugal  —  Treatment  of  the  sirup  —  Making  sugar  from 
the  sugar  beet  —  History  of  the  development  of  the  industry 

—  Use  of  the  diffusion  process  —  Concentration  and  purifica- 
tion of  the  juice  —  Manufacture  of  maple  sugar  —  Adultera- 
tion of  maple  sugar  —  Sorghum  sugar  and  its  manufacture 

—  Molasses  —  Sugar-refining  —  Methods  adopted  in  the  com- 
mercial centers  —  Use  of  the  bone-black  filter  —  Revivifying 
bone  black  —  Use  of  the  vacuum  pan  and  centrifugal  — 
Granulated  sugar — Powdered  and  cube  sugar — Experiments 
to   show  the   properties  of   sugar — Composition    of    raw 
and  of  refined  sugars  —  Food  value  of  sugars  —  Maltose,  its 
source  and  properties  —  Lactose,  method  of   making  and 
properties 185 

CHAPTER  XV 

GLUCOSE  OR  GRAPE-SUGAR  GROUP 

Processes  used  for  the  manufacture  of  glucose  and  its  composi- 
tion —  Uses  of  glucose  —  Healthfulness  of  the  product  — 
Experiments  upon  glucose  —  Invert  sugars  —  Levulose  — 
Honey  —  Composition  and  properties  of  honey  —  Experi- 
ments with  honey 200 

CHAPTER  XVI 

LEAVES,  STALKS,  ROOTS,  ETC.,  USED  AS  FOOD 
Value  of  this  class  of  nutrients  —  Carrots,  parsnips  —  Turnips 
and  beets  —  Leaves  as  food  —  Composition  and  value  of  cab- 
bage—  Greens  —  Asparagus  —  Rhubarb,  etc. — The  use  of 
onions  and  leeks  —  Tomatoes  and  their  use   ....    207 
Irish  moss  and  its  composition  —  Mushrooms  and  toadstools  — 
The  growing  of  mushrooms  and  their  composition  —  The 
selection  of  the  non-poisonous  varieties         ....     210 

CHAPTER   XVTI 

COMPOSITION  AND  FOOD  VALUE  or  FRUITS 
Some  definitions  —  Composition  of  fruit  at  different  periods  of 
growth  —  Change  in  composition  as  illustrated  by  analysis 


CONTENTS  XT 


of  apples  —  The  ripening  of  fruit  —  Table  showing  composi- 
tion of  various  fruits  —  Value  and  properties  of  the  different 
ingredients  in  fruits  —  Malic  acid,  citric  acid,  tartaric  acid 
•with  experiments  —  Effect  of  cooking  upon  fruits  ,  .  212 
Jams  and  jellies  and  their  adulteration  —  Opportunity  for  falsifi- 
cation in  this  material  —  Substitutes  for  jam  and  jelly  upon 
the  market  —  Experiments  upon  adulterated  jellies  —  Fruit 
sirups  —  Flavoring  extracts  .......  219 


CHAPTER 
EDIBLE  FATS  AND  OILS  —  FOOD  VALUE  OP  NUTS 

Composition  of  edible  fats  —  Digestion  of  fats  and  oils  —  Amount 
of  fat  in  different  vegetable  and  animal  substances  —  Use  of 
cotton-seed  oil  in  cooking  —  Use  of  oil  of  cocoanut  —  Lard  — 
Method  of  making  the  different  grades,  such  as  refined  lard, 
kettle-rendered  lard,  neutral  lard  —  Adulteration  of  lard  — 
Manufacture  of  compound  lard,  cottolene,  cottosuet  —  Use 
of  nuts  as  food  —  Composition  of  the  more  important  nuts  — 
Removal  of  excess  of  oil  from  some  varieties  —  Value  of 
almonds  for  food  —  Use  of  peanuts  as  food  ....  223 

NITROGENOUS  FOODS 

CHAPTER  XIX 
MEAT 

Concentration  of  nitrogenous  food  by  animals  —  Importance  of 
nitrogen  in  the  animal  body  —  Classification  of  nitrogenous 
bodies  —  Functions  of  albuminous  substances  —  Structure  of 
lean  meat  —  Constituents  of  meat  —  Composition  of  beef  — 
Use  of  animal  food  in  different  countries  —  Cooking  of  meat 
by  roasting,  broiling,  etc.  —  Beef  extracts  and  their  value  — 
Different  kinds  of  meat  similar  in  composition  —  Fish  as  a 
cheap  and  nutritious  food  —  Characteristics  of  this  food  — 
Fat  and  lean  fish  —  Use  and  food  value  of  oysters  —  Danger 
from  trichina,  tapeworms,  etc.,  in  pork  —  Experiments  upon 
cooking  meat  .........  228 


XVI  CONTENTS 

CHAPTER  XX 
EGGS 

PAGB 

Composition  of  egg  white  and  egg  yolk  —  Use  of  eggs  as  food  — 
Methods  of  preservation  —  Desiccated  eggs — Proper  method 
for  cooking  eggs  —  Experiments  with  egg  white  and  egg  yolk  238 

CHAPTER   XXI 
MILK,  CHEESE,  AND  BUTTER 

Composition  of  milk  of  different  animals  —  Composition  of  vari- 
ous kinds  of  milk  —  Experiments  upon  the  specific  gravity 
of  milk  —  Composition  of  butter  fat  and  method  for  its  de- 
termination —  Use  of  koumiss  —  Experiments  to  determine 
amount  of  butter  fat  and  total  solids  —  Cause  of  the  souring 
of  milk  —  Experiments  with  coagulents  —  Methods  of  raising 
cream  —  Sterilized  and  pasteurized  milk  —  Condensed  milk 

—  Its  composition  —  Nature  of  modified  milk  and  how  it 
is  prepared  —  Experiments   to  detect  milk  adulteration  — 
Cheese  —  The  method  for  its  manufacture —  Description  of 
different  kinds  of  cheese  —  Table  showing  composition  of 
various  cheeses  —  Butter  and  butter  substitutes  —  Conditions 
necessary  for  making  good  butter  —  Renovated  or  process 
butter  —  Manufacture  of  oleomargarin — Materials  used  in 
making  oleomargarin  —  Attitude  of  the  government  toward 

this  industry  —  Experiments  with  butter    ....    242 

CHAPTER  XXH 
NON-ALCOHOLIC  BEVEBAGES 

General  demand  for  beverages  of  this  class  —  Amount  of  tea, 
coffee,  and  cocoa  used  in  the  United  States —  Source  of  tea 

—  Composition  of  green  and  black  tea  —  The  most  important 
constituents  and  their  properties  —  Experiments  upon  mak- 
ing a  decoction  of  tea  and  its  properties  —  Paraguay  tea — 
Coffee-leaf  tea  —  Coffee  —  History  of  its  growth  —  Method 
of  cultivation  and  preparation  of  the  berry  —  Analysis  of 
coffee  —  Effect  of  roasting  —  Adulteration  of  ground  ccffee 

—  How  to  make  the  beverage  —  Coffee  substitutes  —  Cocoa 
and  chocolate  —  History  of  this  product  —  Method  of  grow- 


CONTENTS  XV11 

PAGE 

ing  the  nuts  —  Composition  of  chocolate,  cocoa,  cocoa  shells 

—  Value  of  cocoa  as  a  food  material — Manufacture  of  choco- 
late— Experiments  upon  chocolate  —  The  cola  nut  —  Com- 
parison of  the  effect  of  the  non-intoxicating  beverages  upon 

the  system 257 

CHAPTER  XXIII 
ALCOHOLIC  BEVERAGES 

Use  of  alcohol  from  the  earliest  history  of  the  world  —  Properties 
of  alcohol  —  Consumption  of  alcoholic  liquors  in  different 
countries  —  Classification  of  alcoholic  beverages  into  fer- 
mented, malt,  distilled  liquors,  and  cordials  —  Per  cent  of 
sugar  in  different  fruits  —  Wine  —  Source  of  wine  —  Method 
of  making  —  Fermentation  —  Aging  wine  —  Chemical  reac- 
tion involved  in  wine  making  —  Changes  produced  by  aging 

—  Composition  of  various  wines  —  Classification  of  wines — 
Why  grapes  make  better  wines  than  other  fruits  —  Adultera- 
tion and  plastering  of  wines — Diseases  of  wines  —  Experi- 
ments upon  wine — Cider — Method  of  making — Adulteration 
and  falsification  —  Beer  —  Method  of  making  malt  —  Chemi- 
cal changes  involved  in  manufacture  of  beer  —  Composition 
of  some  malted  liquors  —  Experiments  upon  beer  —  Distilled 
liquors  —  Definition  —  Method  of  making  alcohol  —  Distinc- 
tion between  brandy,  whisky,  rum,  and  gin  —  Adulteration 
of  fermented  liquors  —  Liqueurs  —  Cordials  —  Physiological 
action  of  alcohol 271 

CHAPTER  XXTV 
FOOD  ACCESSORIES 

Difference  between  condiments  and  spices —  Common  adulterants 
of  ground  spices  —  Source  and  properties  of  cloves,  cinna- 
mon, pepper,  ginger,  nutmeg,  mustard^- Experiments  upon 
spices  —  Vinegar  —  Chemical  changes  involved  in  its  manu- 
facture—  Material  used,  such  as  wine,  fruit  spirits,  malt, 
etc.  —  Quick  vinegar  process  —  Experiments  upon  vinegar 

—  Salt  —  Occurrence  of  salt  in  different  parts  of  the  world 

—  Method  of  obtaining  the  commercial  salt  —  Composition 

of  average  samples  —  Uses  of  salt 288 


XV111  CONTENTS 

CHAPTER  XXV 
PRESERVATION  OF  FOODS  —  COLORING  OF  FOOD  PRODUCTS 

PAGE 

Method  of  preservation  of  food  formerly  adopted  and  those  in 
use  at  present  time  —  Conditions  favoring  fermentation  and 
decay  —  Preservation  by  canning  —  Canning  as  carried  on 
in  large  manufactories  —  Experiments  upon  preservation  of 
food  —  Use  of  tin  cans  —  Experiments  upon  the  composi- 
tion of  the  can  —  Recent  use  of  chemical  preservatives  — 
Objection  to  the  use  of  these  substances  —  Use  and  method 
for  detection  of  borax,  sodium  benzoate,  salicylic  acid, 
sodium  sulfite,  and  formaldehyde  —  Coloring  of  food  prod- 
ucts —  Objections  to  this  custom  —  Use  of  copper  to  give  a 
green  color  to  pickles  —  Experiments  upon  food  coloring  .  297 

CHAPTER  XXVI 

ECONOMT  IN  THE  SELECTION  AND  PREPARATION  OF 
FOOD  —  DIETARIES 

Proper  methods  for  cooking  food  —  How  starch  is  affected  by 
heat  —  Changes  which  fats  undergo  in  cooking  and  the  effect 
of  heat  upon  them  —  Leguminous  foods  and  how  they  should 
be  cooked  —  A  large  amount  of  nutriment  at  small  cost — 
Comparison  of  vegetable  and  animal  foods  —  Relation  be- 
tween cost  of  the  food  and  its  nutritive  value  —  Importance 
of  cooking  each  food  in  the  best  way  — The  use  of  a  steam 
cooker  in  economizing  fuel  —  The  Aladdin  oven  as  an  eco- 
nomic kitchen  utensil 308 

Dietaries :  History  of  the  study  of  the  composition  of  food  — 
Experiments  carried  on  by  the  United  States  government 
—  Definition  of  calories  —  Fuel  value  of  different  classes  of 
nutrients  —  Use  of  the  respiration  calorimeter  —  A  study  of 
the  food  of  different  individuals  or  classes  —  Table  showing 
dietaries  used  in  the  United  States  and  abroad  —  Standard 
dietaries  as  estimated  by  different  authorities  —  The  use  of 
smaller  amounts  of  proteids  than  the  accepted  dietary  would 
indicate  —  The  ideal  ration  —  Cost  of  food  and  nutritive 
ratio  —  Per  cent  of  income  expended  for  food  by  people  of 
different  classes 312 

BIBLIOGRAPHY  .        .        .     323 


INTRODUCTION 

A  KNOWLEDGE  of  the  science  of  chemistry  is  necessary 
for  a  proper  understanding  of  so  many  of  the  other  sciences 
that  it  is  not  strange  that  this  subject  is  so  often  required  of 
students  in  the  lower  grades.  To  know  even  the  rudiments 
of  physics,  botany,  biology,  geology,  mineralogy,  or  physi- 
ology, the  student  must  have  a  fair  knowledge  of  chemistry. 

When  we  consider,  however,  the  arts  that  have  to  do  with 
modern  living,  —  the  eating,  drinking,  and  breathing,  all  of 
which  may  be  prosaic  enough  in  their  way,  —  it  is  evident 
that  the  foundation  study  here  also  is  a  knowledge  of  the 
composition  of  the  substances  surrounding  us. 

A  knowledge  of  the  relations  to  health  of  pure  air,  un- 
polluted water,  and  wholesome  food  will  have  much  to  do 
with  improvement  in  sanitary  conditions,  not  only  of  stu- 
dents themselves,  but,  through  them,  of  the  people  at 
large.  The  air  is  usually  said  to  be  free,  but  pure  air  and 
sunshine  cost  money  as  the  crowded  tenements  show.  The 
best  lighted  and  ventilated  rooms  are  worth  the  most. 
Since  physicians  agree  that  impure  air  is  a  predisposing 
cause  of  a  large  per  cent  of  diseases,  it  is  of  the  greatest 
importance  that  a  knowledge  of  the  danger  from  this  source 
be  diffused  among  all  classes  of  people. 

Water  is  furnished  by  the  well  or  cistern  at  the  farm  or 
the  isolated  country  house,  and  for  a  very  large  population 
by  a  corporation  or  by  the  municipality  itself.  Those  who 
use  the  water  from  the  private  source  of  supply  or  those 
who  furnish  it  to  the  multitude  of  the  city,  should  know 


XX  INTRODUCTION 

how  water  becomes  polluted  and  how  to  guard  against 
disease  from  this  source. 

The  food  supply  is  obtained  from  various  sources.  There 
is  a  growing  tendency  to  have  food  prepared  outside  the 
household,  and  the  family  learn  to  depend  on  the  baker,  the 
grocer,  and  the  packing  house  for  their  food.  With  this 
tendency  comes  the  temptation  to  those  who  furnish  food 
ready  prepared  or  dressed,  to  falsify  or  adulterate  it,  be- 
cause they  have  the  opportunity. 

It  is  certainly  time  that  the  people  should  have  some 
practical  knowledge  of  food  and  medicine.  Without  this 
knowledge  they  will  continually  be  imposed  upon  by 
those  who  have  something  to  sell  which  may  be  worthless 
as  a  food,  or  dangerous  as  a  medicine. 

Just  as  society  claims  the  right  to  protect  itself  against 
epidemics,  against  polluted  water,  and  against  smoke  nui- 
sances, so  it  is  learning  that  it  also  has  the  right  to  protect 
itself  against  bad  food.  The  United  States  and  the  various 
state  and  city  governments  have  aided  the  people  generously 
for  the  past  twenty-five  years,  and  by  their  published  analy- 
ses, bulletins,  and  other  literature  have  assisted  notably  in 
molding  public  sentiment  in  favor  of  wholesome  and  un- 
adulterated food.  The  foundation  of  the  present  move- 
ment seems  to  be  publicity. 

Schools  and  colleges  are  beginning  to  see  their  oppor- 
tunity to  impart  a  kind  of  knowledge  that  is  practical  and 
sane,  and  so  we  have  the  manual  training  school  and  the 
agricultural  college,  as  well  as  instruction  in  domestic 
science  in  schools  of  a  lower  grade. 

A  thorough  understanding  of  the  facts  of  applied  chem- 
istry will  not  make  the  skilled  workman,  nor  will  the  theories 
of  chemistry  make  the  accomplished  cook,  but  a  broad  and 
thorough  knowledge  of  the  underlying  principles  will  go 
very  far  toward  developing  common  sense  in  hygiene  and 
in  the  selection  and  preparation  of  food. 


SANITAEY  AND  APPLIED  CHEMISTRY 


PAET  I 

SANITARY  AND  APPLIED   CHEMISTRY 

CHAPTER  I 

THE  ATMOSPHERE 

HISTORY 

THE  early  philosophers  in  the  time  of  Aristotle,  350  B.C., 
thought  there  were  four  elements,  —  earth,  air,  fire,  and 
water,  —  and  that  each  of  these  had  special  properties,  and 
they  also  believed  that  the  air  had  weight.  For  sixteen 
hundred  years  comparatively  nothing  was  done  except  to 
theorize  in  regard  to  the  properties  of  air.  Then  Galileo, 
an  Italian,  showed  that  a  copper  globe  filled  with  air  under 
ordinary  pressure  weighed  less  than  the  same  globe  filled 
with  compressed  air.  Galileo  was  fortunate  in  making  the 
acquaintance  of  Torricelli,  and  at  the  death  of  the  former, 
Torricelli  carried  on  the  experiments.  He  explained  why 
it  was  impossible  to  raise  water  more  than  thirty-three  feet 
in  a  tube  by  suction ;  that  is,  that  there  was  not  sufficient 
pressure  of  the  air  to  force  the  water  higher,  and  he  also 
reasoned  that  a  heavier  liquid,  like  mercury,  could  not  be 
raised  as  far  as  water  by  suction.  He  tried  this  experiment 
and  found  that  mercury  could  be  raised  only  about  thirty 
inches,  and  noticed  that  the  relation  between  the  specific 
gravity  of  mercury  and  that  of  water  was  inversely  propor- 
tional to  the  height  to  which  the  two  liquids  could  be  raised. 
That  is,  water  can  be  raised  13.6  times  as  far  as  mercury. 

B  1 


2  SANITARY   AND   APPLIED   CHEMISTRY 

The  theory  that  air  had  weight,  and  kept  the  mercury  or 
the  water  up  in  the  barometer  tube,  was  not  fully  adopted 
when  Torricelli  died.  Pascal,  who  followed  these  inves- 
tigators, said  that  if  their  theory  was  true,  a  column  of 
mercury  would  fall  when  a  barometer  was  carried  to  an 
elevation,  so  he  secured  the  services  of  a  friend  to  carry  a 
barometer  to  the  top  of  a  mountain  in  France,  and  the  latter 
was  delighted  to  find  that  as  he  ascended  the  mountain  the 
mercury  fell.  It  was  left  to  Boyle  to  use  this  apparatus, 
which  he  called  a  "barometer"  (Gr.  baros,  metroii),  to 
measure  the  weight  of  the  air. 

All  this  time  air  was  regarded  as  a  simple  element,  and  the 
next  epoch  in  its  study  was  the  discovery,  by  Priestley  and 
Scheele  in  1774,  that  it  contained  the  element  oxygen.  It 
was  left  for  the  French  chemist,  Lavoisier,  to  correlate  the 
discoveries  of  several  chemists,  and  to  show  that  when 
oxygen  was  taken  out  of  the  air,  the  gas  that  remained  was 
the  so-called  nitrogen,  discovered  in  1772  by  Rutherford. 
Lavoisier  found  that  by  heating  mercury  in  a  confined 
volume  of  air,  it  would  take  up  a  measured  quantity  of 
oxygen,  and  the  residual  gas  left  in  the  flask,  which  would 
not  support  combustion,  was  nitrogen.  Cavendish  made  a 
large  number  of  experiments  on  the  air,  but  it  was  Bunsen, 
Le  Roy,  and  Regnault  who  showed  that  air  is  not  always 
of  the  same  composition,  though  very  nearly  so,  and  that 
consequently  it  cannot  be  a  chemical  compound,  but  must 
be  a  mixture  of  different  gases.  These  experiments,  made 
about  the  middle  of  the  last  century,  marked  another  im- 
portant period  in  the  study  of  the  atmosphere. 

The  last  era  is  the  recent  discovery  (in  1895  and  the  years 
following),  by  two  Englishmen,  Lord  Rayleigh  and  Pro- 
fessor Ramsay,  of  argon ;  and  later  helium  and  other  gases 
were  discovered  in  the  atmosphere.  The  circumstances  that 
led  to  the  discovery  of  argon  are  interesting.  Lord  Rayleigh 


THE   ATMOSPHERE  3 

noticed  that  the  weight  of  a  liter  of  nitrogen  obtained 
from  chemicals,  as  when  ammonium  nitrite  is  heated, 
is  1.2505  grams,  while  that  obtained  from  nitrogen  of  the 
air  is  1.2572  grams.  It  was  impossible  to  account  for  this 
by  assuming  errors  in  the  weighings,  which  were  made  with 
exceptional  care.  These  men  experimented  with  air  by 
passing  a  strong  electric  spark  through  a  confined  volume 
of  air,  contained  in  a  tube  over  mercury,  thus  causing  some 
oxygen  and  nitrogen  to  unite,  and  forming  an  oxid  of  nitro- 
gen. The  latter  was  absorbed  by  a  solution  of  potassium 
hydroxid,  then  more  oxygen  was  introduced,  and  the  spark- 
ing by  electricity  was  continued,  until  finally  only  a  small 
residue  remained,  which  could  not  be  made  to  combine  with 
oxygen.  The  excess  of  oxygen  was  then  absorbed,  and  the 
residual  gas  was  placed  in  a  Pliicker  tube  under  dimin- 
ished pressure,  and,  while  a  current  of  electricity  was 
passed  through  it,  was  examined  by  means  of  the  spectro- 
scope. The  spectrum  was  different  from  that  of  any  known 
gas.  Other  substances  were  brought  in  contact  with  this 
gas,  but  it  did  not  unite  with  them,  and  the  name  "  argon," 
which  signifies  "  inactive,"  was  given  to  the  gas.  This  gas 
was  also  prepared  from  air,  after  the  oxygen  had  been 
removed,  by  passing  it  over  red-hot  magnesium,  which 
took  out  the  nitrogen  and  left  the  argon. 

A  little  later,  the  element  "helium"  was  found  first  in 
the  mineral  Clevite,  and  afterwards  in  the  air.  This  had  pre- 
viously been  discovered  in  the  atmosphere  of  the  sun  by  the 
examination  of  sunlight  with  a  spectroscope,  and  chem- 
ists were  delighted  to  find  that  the  gas  which  they  obtained 
from  certain  minerals,  and  also  from  mineral  springs,  was 
the  same  as  had  previously  been  discovered  in  the  sun. 
More  recently  the  other  gases,  neon,  krypton,  xenon,  were 
discovered.  Since  liquid  air  can  now  be  made  at  a  compara- 
tively small  expense  in  large  quantities,  these  latter  gases 


4  SANITARY   AND   APPLIED  CHEMISTRY 

may  be  separated  from  it  by  "  fractional  distillation,"  and 
may  thus  be  more  thoroughly  studied. 

CONSTITUENTS  OF  THE  AIE 

The  average  composition  of  moist  air  by  volume  is  as 
follows :  — 

PARTS  PER  1000 

Oxygen 207.7 

Nitrogen .        .    773.6 

Water .        .        .        .        8.4 

Argon 9.4 

Carbon  dioxid       .        ...        .        .        .          .3  to  .4 

Nitric  acid Trace 

Ammonia Trace 

Hydrogen  sulfid     . Trace 

Sulfurous  anhydrid Trace 

Helium .001 

Krypton .001 

Xenon 0005 

Hydrogen 2 

Neon     .        .        .        .        .        .        .        .        .     .01 

Experiment  1.  To  show  the  weight  of  air.  Fill  a  glass 
tube  about  900  mm.  long,  closed  at  one  end,  with  clean,  dry 
mercury,  and  invert  it  over  a  vessel  of  mercury.  Bead  the 
height  of  the  column  by  means  of  a  meter  measure. 

NOTE.  If  a  sufficient  quantity  of  mercury  is  not  at  hand,  this  and 
Experiment  3  may  be  performed  by  the  instructor  only. 

Experiment  2.  Read  a  good  barometer,  and  compare 
reading  with  that  obtained  in  the  tube. 

Experiment  3.  To  show  the  effect  of  moisture  in  air,  or 
the  vapor  tension  of  water,  add  a  small  drop  of  water  to  the 
mercury,  by  putting  it  beneath  the  surface  of  the  mercury 
in  the  tube,  with  a  glass  tube  bent  upward  at  the  lower  end. 
Record  the  difference  of  level. 


THE   ATMOSPHERE  5 

Bacperiment  4.  To  prove  the  composition  of  air,  melt 
some  phosphorus  in  one  end  of  a  100  cc.  eudiometer  tube 
tightly  closed  with  a  soft  cork.  The  phosphorus  may  be 
melted  by  immersing  the  end  of  the  tube  in  boiling  water 
for  a  few  minutes.  Throw  the  phosphorus  along  the  tube 
by  swinging  it,  and  it  should  take  fire.  Immerse  the  corked 
end  of  the  tube  in  a  cylinder  of  water,  remove  the  cork,  and 
the  water  will  rush  in.  When  the  contents  of  the  tube  has 
become  of  the  same  temperature  as  the  air,  read  the  level 
of  the  water  inside  the  tube,  first  making  it  of  the  same 
height  inside  as  outside,  by  lowering  or  raising  the  tube. 
Calculate  the  per  cent  of  oxygen  in  the  air. 

As  previously  stated,  these  gases,  oxygen,  nitrogen,  etc., 
are  mechanically  mixed  in  the  air.  This  may  be  proven  as 
follows :  — 

1st,  Because  the  air  in  different  localities  has  different 

composition. 
2d,   Because  air  dissolved  in  water  is  richer  in  oxygen 

than  ordinary  air. 
3d,   Because  the  mixture  of  oxygen  and  nitrogen  in  the 

proportion  of  air  cannot  be  made  to  combine  by  a 

spark  to  form  air. 
4th,  If  liquid  air  is  allowed  to  evaporate,  the  nitrogen 

goes  off  first,  leaving  nearly  pure  oxygen. 

Air  is  vitiated  or  rendered  too  impure  for  respiration 
from  a  variety  of  causes.  Among  these  may  be  mentioned 
an  increase  in  the  amount  of  carbon  dioxid,  and  a  conse- 
quent decrease  in  the  amount  of  oxygen ;  a  lack  of  sufficient 
moisture,  and  an  excess  of  moisture;  by  the  presence  of 
suspended  impurities  of  a  vegetable,  animal,  or  mineral 
origin;  by  poisonous  gases,  from  illuminating  gas,  sewers, 
or  manufactories;  by  the  presence  of  the  impurities  that 
are  due  to  respiration,  and  by  a  mixture  with  ground  air. 


6  SANITARY   AND   APPLIED   CHEMISTRY 

The  methods  used  for  the  analysis  of  air  'are  usually 
volumetric.  From  a  sanitary  standpoint,  the  most  practical 
thing  is  to  determine  the  amount  of  some  of  the  substances 
which  are  present  in  small  quantity,  but  which  are  really  of 
great  hygienic  importance. 

It  is  assumed  that  we  are  familiar  with  the  properties  of 
oxygen,  a  gas  that  assists  in  combustion,  causes  a  spark  to 
burst  in  a  flame,  and  is  absolutely  necessary  to  respiration. 
The  amount  of  oxygen  found  in  the  air  in  different  localities 
varies,  according  to  Bunsen,  within  narrow  limits  from 
20.97%  to  20.84%.  These  results  were  confirmed  by  Eeg- 
nault,  R.  Angus  Smith,  Leeds,  and  others,  who  made  analy- 
ses of  air  from  different  parts  of  the  world.  In  the  crowded 
tenement  districts  the  air  has  been  found  to  contain  as  low 
as  20.60  %  of  oxygen. 

The  air  as  it  leaves  the  lungs  contains  about  79%  of 
nitrogen  and  argon,  and  only  16  %  of  oxygen,  for  the  air 
instead  of  containing  the  normal  amount  of  carbon  dioxid, 
now  contains  about  4.4  % .  This  oxygen  has  been  consumed 
in  the  vital  processes.  When  the  normal  proportions  of 
the  gases  in  the  atmosphere  are  disturbed,  the  human  sys- 
tem is  very  susceptible  to  it,  and  this  is  one  of  the  causes 
for  discomfort  in  a  crowded  room. 

Nitrogen,  on  the  other  hand,  has  properties  that  are,  to 
some  extent,  opposed  to  those  of  oxygen.  Nitrogen  does  not 
burn,  does  not  support  combustion,  is  not  poisonous,  and  is,  in 
fact,  an  inert  gas.  In  combination,  however,  it  is  of  special 
importance,  as  in  nitrates,  explosives,  coloring  matters,  and 
alkaloids,  as  well  as  in  vegetable  substances,  and  in  nearly 
all  animal  tissues. 

Water  in  the  air  is  necessary  both  for  the  growth  of 
vegetable  and  animal  life.  The  amount  of  vapor  that 
air  holds  in  suspension  depends,  of  course,  upon  the  tem- 
perature. The  higher  the  temperature,  the  greater  the 


THE   ATMOSPHERE  7 

amount  of  moisture  the  air  will  hold  without  precipitation. 
Where  air  contains  as  much  moisture  as,  at  a  given  temper- 
ature, it  is  capable  of  holding,  it  is  said  to  be  saturated. 
Humidity  has  reference  not  to  the  actual  amount  of  vapor 
present,  but  to  the  proportion  which  this  bears  to  the  pos- 
sible maximum  at  that  temperature. 

At  0°  C.,  a  cubic  meter  of  air  will  hold  only  4.87  g.  of 
water;  at  10°  C.,  9.92  g. ;  at  15°  C.,  12.76  g. ;  at  20°  C., 
17.16  g. ;  and  at  32°  C.,  33.92  g. 

If  the  air  is  absolutely  dry,  plants  wither  and  die,  and 
animals  do  not  thrive  since  they  lose  water  too  rapidly  by 
its  evaporation.  The  amount  of  moisture  in  the  air  varies 
from  -g-^th  to  ^^th  of  the  volume,  and  from  65  %  to 
75  %  of  saturation  is  regarded  as  most  beneficial  to  health. 
If  the  humidity  of  the  air  is  90  %  of  saturation,  and  the 
temperature  is  90°  F.,  the  conditions  are  almost  unbearable, 
while  at  the  same  temperature,  with  50  %  of  humidity,  it 
is  not  uncomfortable.  Air  that  is  saturated  with  moisture 
does  not  permit  the  heat  of  the  earth  to  radiate  so  rapidly. 
At  night,  as  the  air  cools,  we  get  a  deposit  of  dew.  It  is 
well  to  remember  that  the  "  dew-point "  or  the  temperature 
at  which  a  deposit  of  moisture  begins  varies  with  the  amount 
of  moisture  in  the  air.  The  earth  cools  more  rapidly  on  clear 
nights,  hence  in  cold  weather  there  is  greater  danger  of  frost. 
The  amount  of  moisture  thrown  off  from  the  lungs  and  skin 
is  about  one  third  of  that  taken  in  with  the  food.  This  would 
mean  that  from  1|  to  2  Ib.  of  water  would  be  given  off  per 
capita  every  24  hours.  Moist  climates  are  adapted  to  the 
treatment  of  certain  diseases,  while  we  are  familiar  with 
the  action  of  dry  air,  such  as  that  of  Colorado,  Arizona,  and 
California,  in  the  treatment  of  tuberculosis. 

As  air  is  essentially  a  mixture  of  one  part  of  oxygen  with 
four  parts  of  nitrogen  and  a  varying  amount  of  water  vapor, 
the  weight  of  a  liter  of  air  would  be  equal  to  the  sum  of 


8  SANITARY   AND   APPLIED   CHEMISTRY 

these  constituents,  and  the  way  in  which  this  weight  will 
vary  can  be  seen  from  the  following  figures :  — 

The  weight  of  a  liter  of  nitrogen  is  ...     1.25  grams 
The  weight  of  a  liter  of  oxygen  is    ...     1.43      " 
The  weight  of  a  liter  of  water  vapor  is      .       .81      " 

From  the  composition  of  the  air  above  noted,  a  liter  of  dry 
air  would  contain  practically 

800  cc.  of  nitrogen  weighing  .     .     .     1.000  g.,  and 
200  cc.  of  oxygen  weighing     .     .     .       .286  g. 

Giving  a  total  weight  of  air  as    .     .     1.286  g. 

Since  water  vapor  is  lighter  than  either  nitrogen  or 
oxygen,  and  since  it  displaces  its  own  volume  of  these  other 
gases,  air  containing  water  vapor  will  be  lighter  than  an 
equal  volume  of  dry  air. 

To  illustrate:  Suppose  we  have  a  sample  of  air  con- 
taining 5  %  of  water  vapor,  then  a  liter  of  this  air  would 
contain 

760  cc.  of  nitrogen  weighing      .     .       .950    g.,  and 
190  cc.  of  oxygen  weighing  .     .     .       .272    g.,  and 
50  cc.  of  water  vapor  weighing     .       .0405  g. 

Total 1.2625  g. 

As  the  barometer  is  the  measure  of  the  weight  of  air,  a 
column  of  moist  air  of  a  given  height  will  weigh  less  than 
a  column  of  dry  air ;  we  say  the  barometer  falls  before  a 
storm  as  there  is  more  moisture  in  the  air.  It  should 
be  noted  that  the  weight  of  the  air  at  any  time  or  place  also 
depends  on  the  temperature. 

Experiment  5.  To  show  the  presence  of  moisture  in  the 
air,  fill  a  flask  of  about  1  liter  capacity  with  pounded 


THE  ATMOSPHERE  9 

ice  or  snow.  Clean  it  thoroughly  on  the  outside  and 
wipe  it  dry.  Suspend  it  in  the  room  and  notice  after 
a  short  time  the  abundant  deposit  of  moisture  from  the 
air. 

Experiment  6.  Suspend  two  thermometers  that  read  alike 
side  by  side  on  the  iron  stand  in  the  laboratory.  Make  a 
note  of  the  readings.  Fasten  about  the  bulb  of  one  of  them 
by  means  of  a  rubber  band  a  wad  of  cotton  that  has  been 
thoroughly  soaked  in  water.  Note  after  a  short  time  the 
difference  in  temperature  of  the  two  thermometers.  Will 
there  be  this  difference  if  the  air  is  absolutely  saturated 
with  moisture? 

Carbon  dioxid  (C02)  finds  its  way  into  the  air :  — 

1.  By  combustion. 

2.  By  respiration. 

3.  By  the  decay  of  vegetable  matter. 

4.  By  chemical  action. 

5.  By  volcanic  action. 

6.  By  the  escape  of  ground  air. 

This  gas  is  not  poisonous,  as  this  term  is  ordinarily  used, 
but  animals  may  be  said  to  drown  in  carbon  dioxid  gas. 
The  amount  of  this  gas  in  1000  parts  of  air  varies  in  dif- 
ferent places :  for  instance,  in  Munich  it  was  found  to  be 
.051 ;  in  Scotland,  .053 ;  on  London  streets,  .038 ;  at  Lake 
Geneva,  .044.  This  is  for  the  outdoor  air.  More  recent 
investigations  show  that  normal  outdoor  air  contains  between 
.03  and  .04  parts  of  carbon  dioxid.  The  air  in  crowded 
rooms  is  frequently  extremely  impure,  as  shown  by  the 
following  analyses 1 :  — 

1  Pox,  "  Sanitary  Examination  of  Water,  Air,  and  Food,"  p.  204. 


10  SANITARY   AND   APPLIED   CHEMISTRY 

CAKBON  DIOXID  IN  CLOSED  ROOMS 

PERCENTAGE  BY  VOLUME 

A  schoolroom  in  England  contained  .  .  .241 
Sitting  room  in  a  private  house  .  .  .  .304 

Public  library 206 

Courthouse  gallery .290 

Printing  office         .        .    • 149 

Tailor's  workshop  . 306 

Boot  and  shoe  finisher's  shop        .        .        .        .528 

Surrey  Theater 218 

Standard  Theater 320 

Girls'  schoolroom 723 

Schoolroom  in  New  York  City  .  .  .  .280 
Bedroom  with  closed  windows  .  .  .  .230 
Average  of  339  experiments  in  mines  .  .  .785 
Sleeping  cabin  of  a  canal  boat  .  .  .  .950 

It  is  no  doubt  true  that  the  amount  of  carbon  dioxid  in 
the  air  has  something  to  do  with  the  disagreeable  sensations 
experienced  in  a  crowded  room. 

Some  of  these  are :  — 
Headache 
Stupor 
Kestlessness 

Craving  for  excitement 
Fainting 
Nausea 

Lowered  Vitality. 

According  to  the  experiments  by  Drs.  Billings,  Mitchell, 
and  Bergay,  it  is  shown  that  the  disagreeable  effects  pro- 
duced upon  the  system  by  impure  air  are  due  to  the  fol- 
lowing causes :  the  reduction  in  the  amount  of  oxygen, 
the  increase  of  carbon  dioxid,  excess  of  moisture,  the  high 
temperature,  the  dust  and  disagreeable  odors,  in  fact  to  all 
these  combined. 


THE   ATMOSPHERE  11 

We  know  that  considerable  pure  carbon  dioxid  is  not 
especially  injurious,  as  workmen  in  breweries  and  other 
manufactories  are  not  affected  by  even  a  larger  amount  of 
carbon  dioxid  than  is  found  in  the  air  of  a  crowded 
room. 

According  to  the  experiment  of  Cowles  and  Feilmann,1 
air  that  contains  14%  of  carbon  dioxid  and  has  remain- 
ing only  18.1%  of  oxygen,  will  extinguish  a  candle  flame. 
In  the  absence  of  carbon  dioxid  air  to  which  22%  of  nitro- 
gen has  been  added  will  extinguish  a  candle  flame.  Ex- 
pired air  has  about  the  same  composition  as  that  produced 
by  the  burning  of  a  candle  in  an  inclosed  space  until  the 
candle  goes  out.  As  an  atmosphere,  even  as  impure  as  this, 
could  be  breathed  without  causing  insensibility,  the  common 
test  for  the  air  of  a  well,  by  letting  down  a  burning  candle, 
is  within  the  limit  of  safety. 

For  the  determination  of  carbon  dioxid,  many  forms  of 
apparatus  have  been  invented.  Usually  a  measured  amount 
of  air  is  passed  through  a  solution  of  barium  hydroxid  or 
calcium  hydroxid,  and  the  barium  or  calcium  carbonate  thus 
formed  is  filtered  off  and  weighed.  The  reaction,  where 
barium  hydroxid  is  used,  is  as  follows  :  — 

Ba(OH)2  +  C02  =  BaC03  +  H20. 

Rather  an  ingenious  apparatus  is  put  upon  the  market  espe- 
cially for  the  use  of  Boards  of  Health  in  testing  the  air 
of  schoolrooms.  This  is  known  as  Wolpert's  apparatus. 
The  principle  of  this  apparatus  is  the  same  as  that  pre- 
viously noted,  except  the  amount  of  air  is  measured  by  a 
number  of  fillings  of  the  bulb,  and  the  density  of  the  pre- 
cipitate by  referring  to  a  table  gives  an  index  to  the  amount 
of  carbon  dioxid. 

lJour.  Soc.  Chem.  Ind.,  Vol.  13,  p.  1155 ;  Vol.  14,  p.  345. 


12  SANITAEY   AND   APPLIED   CHEMISTRY 

Experiment  7.  To  show  the  production  of  carbon  dioxid 
by  combustion,  attach  a  funnel,  by  means  of  a  tube  bent 
twice  at  right  angles,  like  an  inverted  "  fl ,"  to  a  Woulf  flask 
containing  limewater.  Through  the  other  opening  in  the 
flask  put  a  cork  and  glass  tube,  and  aspirate  air  through  the 
limewater.  Place  a  lighted  candle  beneath  the  funnel, 
and  notice  the  formation  of  carbon  dioxid.  Write  the 
equation  for  the  combustion  of  the  carbon  of  the  candle, 
and  for  the  precipitation  in  limewater. 

Experiment  8.  Repeat  the  above  experiment  with  a  small 
jet  of  illuminating  gas  under  the  funnel,  and  notice  whether 
the  limewater  becomes  as  quickly  turbid  as  with  the  candle. 

Experiment  9.  To  show  the  presence  of  carbon  dioxid  in 
the  breath,  arrange  an  apparatus  by  the  use  of  two  Erlen- 
meyer  flasks,  fitted  with  corks,  each  provided  with  two  holes 
fitted  with  glass  tubes,  so  arranged  that  air  may  be  drawn  in 
through  limewater  in  one  flask  at  each  inspiration,  and  may 
be  passed  out  through  limewater  in  the  other  flask  at  each 
expiration.  Notice  that  the  limewater  is  turbid  in  one 
flask  and  not  in  the  other.  Why? 

Experiment  10.  To  determine  the  amount  of  carbon  di- 
oxid gas  in  air,  use  Wolpert's  apparatus,  which  depends 
on  the  turbidity  produced  by  carbon  dioxid  in  limewater, 
making  tests  in  different  rooms. 

Experiment  11.  Determine  the  strength  of  a  solution  of 
limewater  or  baryta  water  against  a  standard  solution  of 
oxalic  acid,  containing  2.84  grams  of  oxalic  acid  per  liter,  by 
placing  25  cc.  of  limewater  in  a  porcelain  dish,  and  running 
into  this,  through  a  graduated  burette,  enough  oxalic  acid 
to  exactly  neutralize  it,  using  a  strip  of  turmeric  paper  as  an 
outside  indicator.  This  equation  shows  what  takes  place :  — 

H AC202  +  Ca(OH)2  =  Ca02C202  +  2  H20. 


THE   ATMOSPHERE  13 

Find  the  exact  capacity  of  a  glass-stoppered  bottle  of  4-6 
liters  capacity  ;  measure  into  this  bottle  50  cc.  of  limewater, 
shake,  and  set  aside  for  6  or  8  hours.  Take  out  with  a 
pipette  25  cc.  of  the  limewater  without  shaking,  so  as  to 
get  as  little  calcium  carbonate  as  possible,  and  titrate  this 
with  the  standard  oxalic  acid ;  and  the  difference  between 
the  amount  used  and  the  amount  required  to  neutralize 
25  cc.  of  the  untreated  limewater  represents  the  effect  due 
to  the  carbon  dioxid  gas  in  the  air.  The  action  of  the  carbon 
dioxid  on  the  limewater  is  represented  by  the  equation :  — 

C02  +  Ca  (OH)a  =  CaC03  +  H20. 

The  oxalic  acid  used  is  of  such  strength  that  1  cc.  cor- 
responds to  0.5  cc.  of  carbon  dioxid  gas.  Subtract  50  cc. 
from  the  capacity  of  the  bottle  for  the  space  occupied  by 
the  limewater.  Calculate  the  parts  of  carbon  dioxid  per 
10,000  parts  of  air.  This  may  be  reduced  to  standard  con- 
ditions of  temperature  and  pressure  by  the  usual  methods. 
(See  "Public  Health  Laboratory  Work,"  Kenwood,  p.  194.) 

An  example  of  the  calculation  is  as  follows :  suppose  it 
required  30  cc.  of  oxalic  acid  solution  to  neutralize  25  cc. 
of  limewater,  and  the  25  cc.  of  limewater  from  the  bottle 
of  air  is  neutralized  by,  say,  27  cc.  of  the  oxalic  acid  solu- 
tion. This  means  that  the  carbon  dioxid  in  the  air  was 
equivalent  to  3  cc.  of  oxalic  acid  solution.  1  cc.  of  this 
solution  =  0.5  of  carbon  dioxid,  then  3  cc.  =  1.5  cc.,  which 
multiplied  by  2  for  the  other  25  cc.  of  limewater  in  the 
bottle  gives  3  cc.  of  carbon  dioxid.  If  the  capacity  of  the 
bottle  was  4000  cc.,  subtract  50  cc.  from  this  =  3950  = 
volume  of  the  air  taken.  Hence  we  calculate  .0759%  of 
carbon  dioxid  in  the  air. 

Carbon  monoxid  (CO)  is  sometimes  found  in  the  air  of 
inhabited  rooms,  on  account  of  insufficient  ventilation  or 
leaky  joints  in  furnaces.  Eed-hot  cast  iron  will  also  trans- 


14  SANITARY   AND   APPLIED   CHEMISTRY 

rait  the  gas.  As  it  is  extremely  poisonous,  —  less  than  one 
half  of  one  per  cent  in  air  behag  fatal  to  human  life,  —  it  is 
of  the  utmost  importance  that  it  be  excluded  from  the  air 
of  our  dwellings.  Fortunately,  although  carbon  monoxid 
itself  has  no  odor,  it  is  usually  mixed  with  some  other  gas 
that  has  a  decided  odor.  In  coal  gas  it  is  mixed  with  the 
sulphur  compounds  which  are  so  readily  detected  by  smell, 
and  in  escaping  furnace  gases  it  is  usually  accompanied  by 
sulfur  dioxid,  which  has  the  familiar  odor  of  a  burning 
match.  When  formed  by  burning  charcoal,  there  is  scarcely 
a  perceptible  odor.  (See  Ventilation,  p.  38.) 

Nitric  acid  in  the  air  is  largely  a  result  of  the  oxidation 
of  the  ammonia.  Some  nitrogen  oxids  are  formed  from 
free  nitrogen  by  the  lightning  flashes  in  the  air.  The 
nitric  acid,  when  washed  into  the  soil  by  the  rains,  is  of 
great  value  as  a  fertilizer  for  growing  plants. 

Ammonia  is  formed  partly  by  the  decay  of  vegetable 
and  animal  matter  in  the  soil  and  partly  by  other  chemical 
processes.  Ammonia  would  naturally  unite  with  carbon 
dioxid,  making  ammonium  carbonate,  or  with  the  nitric  acid, 
making  ammonium  nitrate;  and  both  the  acid  and  the 
base  in  this  latter  salt  are  useful  when  washed  down  by  the 
rain,  in  enriching  the  soil.  The  amount  of  ammonia  varies 
from  0.1  to  100  volumes  in  a  million  volumes  of  air. 

Hydrogen  sulfid  will  not  ordinarily  be  found  in  pure  air, 
but  in  cities,  where  there  is  decomposition  of  organic  matter 
and  sewer  gas,  it  may  be  frequently  detected  by  its  disagree- 
able odor.  Sulfurous  anhydrid  is  not  a  constituent  of  the 
pure  air  of  the  country,  but  where  soft  coal  is  burned,  or  where 
there  are  manufactories  operating,  this  gas  will  be  found. 
Sulfur  dioxid  is  quite  noticeable  in  the  vicinity  of  chemical 
works,  especially  where  zinc,  lead,  and  copper  ores  are  smelted. 
An  extremely  small  quantity  of  the  gas  in  the  air  is  fatal 
to  vegetable  life,  so  that  trees  and  shrubs  in  the  vicinity 


THE  ATMOSPHERE  '  15 

of  smelters  and  chemical  works,  especially  on  the  side  toward 
which  the  prevalent  wind  carries  the  fumes,  are  killed. 

There  is  an  interesting  form  of  oxygen  known  as  ozone. 
It  was  noticed  many  years  ago  that  a  peculiar  smell  ac- 
companied a  thunderstorm,  and  this  as  well  as  the  lightning 
was  ascribed  to  evil  spirits.  As  early  as  1785  Van  Marum 
noticed  a  peculiar  odor  in  the  vicinity  of  an  electrical 
machine,  and  recognized  that  it  was  the  same  as  that  ac- 
companying lightning  discharges.  It  was  not  till  1840, 
however,  that  Schonbein,  a  Swiss  chemist,  discovered  ozone, 
and  showed  that  electricity  changes  oxygen  to  ozone. 

In  addition  to  the  production  of  ozone  by  electrical  dis- 
charges, it  is  formed  in  many  other  ways,  as  by  the  slow 
oxidation  of  phosphorus,  by  the  partial  combustion  of  ether, 
and  by  the  action  of  sulf  uric  acid  on  potassium  permanganate 
or  on  barium  dioxid.  Ozone  slowly  changes  back  to  oxygen 
at  100°  C.  and  rapidly  at  300°  C.  It  has  been  shown  that  one 
volume  of  ozone  can  be  smelled  if  present  in  21  million 
volumes  of  air.  When  a  known  volume  of  ozone  is  changed 
back  to  oxygen,  there  is  an  increase  in  volume.  This  is  due 
to  the  fact  that  a  molecule  of  ozone  contains  three  atoms, 

thus  [  \7"P  ]  5  and  a  molecule  of  oxygen,  two  atoms  (0  =  0). 

Ozone  is  a  very  powerful  oxidizing  agent  and  on  this  account 
has  been  considered  extremely  useful  in  the  purification  of 
the  air  and  the  oxidation  of  its  impurities. 

It  was  for  a  long  time  supposed  that  the  test  with  "  ozone 
paper"  was  a  positive  proof  that  ozone  existed  in  the  air, 
but  as  other  substances,  such  as  some  of  the  oxids  of  nitro- 
gen, color  ozone  paper  in  a  similar  way,  there  is  still  some 
doubt  as  to  whether  it  exists  in  appreciable  quantities  in  the 
atmosphere. 

Hydrogen  peroxid  (H202)  is  a  powerful  oxidizing  agent 
which  is  present  in  the  air,  and  in  rain  and  snow  water.  It 


16  SANITARY   AND   APPLIED   CHEMISTRY 

is  probable  that  some  of  the  effects  ascribed  to  ozone  are 
really  due  to  hydrogen  peroxid,  on  account  of  its  similar 
oxidizing  action.  The  use  of  this  substance  as  a  disinfectant 
is  well  known. 

Experiment  12.  To  make  "  ozone  paper,"  mix  about  5  g. 
of  starch  with  20  cc.  of  cold  distilled  water.  Pour  this  into 
a  beaker  containing  100  cc.  of  boiling  water,  in  which  has 
been  dissolved  about  a  gram  of  potassium  iodid.  Heat  the 
mixture  for  a  moment.  Soak  strips  of  white  filter  paper  in 
this  solution  and  allow  them  to  dry  in  pure  air. 

Experiment  13.  To  make  ozone,  turn  a  static  electrical 
machine  and  test  the  air  in  the  vicinity  by  means  of  moist 
ozone  paper.  The  paper  should  turn  blue. 

Experiment  14.  Heat  a  large  glass  rod  in  a  Bunsen 
burner.  Pour  a  few  drops  of  ether  into  a  medium-sized 
beaker  and  move  the  rod  around  in  the  vapor  of  ether.  Test 
this  vapor  for  ozone,  which  with  other  products  is  probably 
present. 

Experiment  15.  Cut  some  phosphorus  in  thin  slices  under 
water,  and  place  them  in  a  cylinder  with  a  little  warm  water 
in  the  bottom,  but  not  enough  to  cover  the  phosphorus. 
Suspend  some  pieces  of  moist  ozone  paper  in  the  jar  and 
place  a  cover  over  it.  After  a  time  the  paper  will  turn  blue, 
showing  the  presence  of  ozone. 

SUBSTANCES    IN    SUSPENSION    IN    THE    AIR 

Although  the  air  is  apparently  clear  and  transparent,  yet 
we  have  only  to  admit  a  ray  of  sunlight  into  a  room  to  see 
the  dust  which  is  in  the  air.  "Minute  particles  of  any- 
thing and  everything  that  exists  upon  the  earth  are  liable 


THE  ATMOSPHERE  17 

to  be  mingled  in  the  air  that  rests  on  it.  These  suspended 
matters  are  furnished  by  animal,  vegetable,  and  mineral 
kingdoms." 1  We  get,  in  the  animal  kingdom,  the  debris  of 
little  creatures  suspended  in  the  atmosphere  —  eggs  and 
other  substances.  From  the  vegetable  kingdom  we  get 
spores  of  fungi,  bacteria,  pollen  of  plants,  seeds  of  all  kinds, 
particles  of  straw,  etc.  From  the  soil,  the  dust  of  inorganic 
composition,  such  as  sand,  iron  oxid,  lime,  mud  from  vol- 
canoes, particles  of  carbon,  sulfur,  and  in  the  vicinity  of  the 
ocean,  sodium  chlorid  and  other  minerals  carried  long  dis- 
tances by  the  wind. 

The  air  of  sick  rooms,  hospitals,  and  prisons  has  been 
carefully  examined,  and  a  microscopic  study  has  been  made 
of  the  dust  collected.  It  has  been  found  to  contain  a  variety 
of  organic  matter.  The  first  method  of  examination  is  by 
passing  a  known  quantity  of  air  through  a  tube  closely 
packed  with  sterilized  cotton,  and  then  washing  the  cotton 
and  examining  the  wash  water.  By  this  means  we  can 
arrive  at  the  number  of  spores  per  liter  of  air.  A  known 
volume  of  air  may  be  drawn  through  sand  or  sugar  and  steril- 
ized liquid  gelatine  added  to  this,  and  finally  the  number  of 
colonies  in  the  gelatine  may  be  counted.  A  more  convenient 
method,  however,  is  what  is  known  as  the  plating  method, 
in  which  we  pour  into  a  series  of  shallow  glass  vessels  a 
nutrient  medium  which  becomes  solid  on  cooling.  To  this 
the  dust  particles  readily  adhere.  This  gives  a  moist,  sticky 
surface,  which  can  be  easily  protected  by  tightly  fitting 
covers.  When  we  desire  to  examine  the  air  in  any  locality, 
one  of  these  vessels  is  opened  and  exposed  to  the  air  for 
a  specified  time,  say  25  min.  In  this  way  it  is  possible 
to  compare  the  air  in  different  localities.  By  counting  colo- 
nies, each  one  of  which  presumably  consists  of  the  off- 
spring of  a  single  germ,  the  following  numbers  of  bacteria 

1  Fox,  "Water,  Air,  and  Food,"  p.  264. 


18  SANITARY   AND   APPLIED   CHEMISTRY 

were    found    under    different    conditions    in    New    York 
City:  — 

Central  Park,  dust  blowing 49 

Union  Square .  214 

In  a  private  house      .......  34 

Dry  goods  store  ........  199 

Broadway  and  35th  St.      .     \        .        .        .        .  941 

When  the  street  was  being  cleaned    ....  5810 

In  a  house  called  clean 180 

In  a  filthy  house 900 

In  a  dirty  schoolroom  with  natural  ventilation .        .  2000 

Average  in  hospitals  and  dispensatories    .        .        .  127 

There  are  in  fact  more  living  microorganisms  in  the  air 
than  the  above  results  would  indicate,  for  many  germs  do 
not  find  in  the  nutrient  medium  conditions  favorable  to 
development.  It  is  understood  that  these  organisms  are 
of  widely  different  character  and  they  are  generally  either 
molds,  yeasts,  or  bacteria.  It  is  estimated  that  in  the 
open  country  in  a  cubic  inch  of  air  there  may  be  2000  dust 
particles,  3,000,000  in  the  air  of  city  streets,  and  30,000,000 
in  that  of  inhabited  rooms.1  While  microorganisms  are 
very  abundant  in  the  air  of  towns,  there  are  hardly  any 
at  great  heights  and  at  sea.  Pasteur  exposed  a  large  num- 
ber of  flasks  of  broth  at  an  altitude  of  6000  feet,  and  ob- 
tained a  growth  in  but  one.  Tyndall  exposed  twenty-seven 
flasks  at  8000  feet  and  got  no  growth  whatever.  Dr.  Fisher 
has  shown  that  on  the  ocean  120  miles  from  land  the  air  is 
usually  free  from  organisms  and  that  at  a  lesser  distance 
—  90  miles  for  example  —  it  contains  but  few.  * 

Dust,  however,  is  of  great  importance  on  account  of  its  in- 
fluence upon  the  precipitation  of  rain,  upon  clouds  and  fog. 

There  are  certain  diseases,  such  as  consumption,  diphtheria, 

1  Nature,  Vol.  31,  p.  265  ;  Vol.  41,  p.  394. 
a  Harrington,  "Practical  Hygiene,"  p.  233. 


THE  ATMOSPHERE  19 

smallpox,  yellow  fever,  Asiatic  cholera,  scarlatina,  measles, 
etc.,  which  are  called  infectious,  and  which  are  often  propa- 
gated by  bacteria  in  the  air.  Much  attention  has  been  paid 
to  the  propagation  of  consumption,  and  the  Bacillus  tubercu- 
losis has  been  quite  thoroughly  studied.  It  is  stated  that  in 
Europe  about  a  million  persons  die  annually  from  consump- 
tion, and  one  tenth  of  all  the  people  of  the  civilized  world 
fall  victims  to  this  disease.  Dr.  Francine  ( J.  Am.  Med.  Ass'n., 
1905)  says  that  110,000  persons  die  every  year  in  America 
from  consumption.  This  is  a  disease  in  which  the  germs 
from  the  dry  sputa  are  carried  in  the  air,  lodged  in  the  air 
passages,  and  if  they  find  the  system  in  the  right  con- 
dition, they  commence  to  grow  and  carry  on  their  deadly 
work. 

A  few  years  ago  there  was  a  great  outcry  against  arsenic 
in  wall  paper,  and  it  was  said  that  the  dust  of  many  rooms, 
in  which  the  walls  were  hung  with  ordinary  paper,  was  laden 
with  arsenic.  An  excellent  article  on  this  subject  appeared 
in  the  Keport  of  the  Massachusetts  Board  of  Health  for  1883. 
The  agitation  of  those  times  no  doubt  caused  the  manufac- 
turers to  substitute  other  coloring  matters  in  the  place  of 
arsenical,  so  that  at  the  present  time,  it  is  very  unusual 
to  find  a  wall  paper  that  contains  arsenic. 

Experiment  16.  To  test  for  arsenic  in  paper  or  in  fabrics, 
cut  the  paper  or  green  cloth  into  shreds,  and  boil  this  in  a 
test  tube,  half  full  of  water.  Add  to  this  about  10%  of 
strong  hydrochloric  acid  and  a  very  small,  bright  piece  of 
copper  foil.  Boil  the  liquid  for  at  least  five  minutes  and 
notice  if  there  is  any  dark  coloration  on  the  copper.  When 
no  coloration  appears,  arsenic  is  absent.  If  there  is  a  colora- 
tion or  deposit,  remove  the  piece  of  copper  carefully  and 
wash  thoroughly.  Dry  it  on  a  piece  of  filter  paper  over  a 
lamp  and  then  place  it  in  a  matrass,  and  heat  cautiously. 


20  SANITARY   AND   APPLIED   CHEMISTRY 

If  arsenic  is  present,  there  will  be  a  sublimate  of  crystals  oi 
arsenious  oxid  (As203)  on  the  inside  of  the  tube.  Examine 
these  crystals  with  a  lens  and  notice  also  if  they  reflect  light 
or  show  triangular  faces. 

INJURIOUS   TRADES 

There  are  many  trades  in  which  the  health  of  the  work- 
men suffers  from  dust  or  injurious  gases.  Dr.  Hirt  has 
studied  the  effect  of  various  trades  on  the  health  of  the 
workmen  in  Germany.  He  made  a  particular  study  of  con- 
sumption among  the  workmen,  and  gives  the  following  as 
a  list  of  the  most  injurious  trades :  flint  cutting,  needle 
and  file  making,  lithographing,  binding,  brush  making, 
stone  cutting,  grindstone  cutting,  type  founding,  cigar  mak- 
ing, molding,  glass  working,  dyeing,  and  weaving.  The 
sharp  mineral  dust  is  by  far  the  most  injurious.  The  worst 
vegetable  dust  is  cotton  fiber,  and  this  produces  great  mor- 
tality, especially  among  women.  The  mortality  is  probably 
increased  on  account  of  the  high  temperature  and  lack  of 
ventilation  in  the  manufactories  where  they  are  obliged 
to  work. 

GROUND  AIR 

Air  is  contained  in  the  ground  sometimes  to  a  depth  of 
20  feet.  It  is  forced  into  the  ground  both  by  its  weight  and 
by  the  pressure  of  strong  winds.  Pettenkofer  found  in 
1870  that  the  air  contained  in  the  ground  is  not  as  pure 
as  ordinary  air.  A  comparison  of  dry  ground  air  with  ordi- 
nary dry  air  is  given  by  Price.1 

AVERAGE  COMPOSITION  or  ATMOSPHERIC  AIR  iw  100  VOLUMES 

Nitrogen 79.00% 

Oxygen 20.96% 

Carbon  dioxid 04  % 

1  "Handbook  of  Sanitation,"  p.  3. 


THE  ATMOSPHERE  21 

AVERAGE  COMPOSITION  OF  GROUND  AIR 
Nitrogen      .        .        .        .        .        .        .   -    .    79.00% 

Oxygen        .        .        .        .        .        ,        .        .     10.35% 

Carbon  dioxid .9.74% 

The  excess  of  carbon  dioxid  is  due  to  decay  of  organic 
matter  that  has  taken  place  in  the  soil,  and  the  decrease  in 
oxygen  is  due  to  the  fact  that  it  has  been  used  up  by  the 
bacteria  and  in  various  processes  of  oxidation.  This  air  also 
contains  a  large  number  of  bacteria,  and  other  organic  forms 
of  life.  When  we  remember  that  a  cubic  centimeter  of  earth 
contains  from  200,000  to  1,000,000  bacteria,  the  opportuni- 
ties for  contamination  of  the  ground  air  are  apparent.  The 
air  of  virgin  soil  is  usually  more  free  from  organic  impurities 
than  the  air  from  the  ground  of  thickly  populated  districts, 
and  the  difference  can  be  readily  understood  when  we  consider 
the  material  which  is  liable  to  collect  in  or  filter  through  the 
soil  of  a  city.  Fatal  results  have  sometimes  followed  the 
breathing  of  air  poisoned  by  the  decaying  of  organic  matter. 
Sir  Henry  Thompson  states  that  gravediggers  have  died 
while  digging  in  the  region  of  vaults  and  cemeteries.1  If 
houses  are  built  upon  the  so-called  "  made  "  land  that  has 
been  filled  in  with  all  sorts  of  refuse  from  the  city  and  from 
manufactories,  the  air  that  comes  into  the  rooms  is  liable 
to  be  contaminated  and  to  be  deficient  in  oxygen.  On 
account  of  the  vitiation  of  air  by  decaying  organic  matter, 
in  large  cities,  cremation  has  been  quite  extensively  advo- 
cated and  is  no  doubt  an  excellent  method  for  the  disposal 
of  garbage  and  dead  bodies. 

OFFENSIVE   GASES 

In  the  ordinary  apartment  there  is  little  danger  of  injury 
from  poisonous  gases.  In  the  centers  of  trade  the  gases 

1  "Cremation,"  E.  E.  Williams,  p.  44. 


22  SANITARY  AND   APPLIED   CHEMISTRY 

from  some  manufactories  would  be  offensive,  if  they  were 
taken  into  the  lungs,  but  they  are  rapidly  diffused  through 
the  atmosphere.  Even  sewer  gas,  which  is  usually  con- 
sidered so  dangerous,  has  been  shown  frequently  to  contain 
a  less  number  of  microorganisms  than  the  outside  air.  This 
gas  is,  of  course,  disagreeable,  often  lacking  in  oxygen,  and 
should  by  no  means  be  allowed  to  escape  into  a  dwelling. 


CHAPTER  II 
FUELS 

IN  the  production  of  heat  for  ordinary  purposes,  such 
fuels  as  wood,  charcoal,  peat,  lignite,  bituminous  coal,  cannel 
coal,  semianthracite,  anthracite,  coal  gas,  and  natural  gas 
are  used.  Wood  spirit,  denaturized  alcohol,  common  alcohol, 
gasoline,  and  kerosene  find  a  limited  use;  and  electricity 
may  be  used  for  heating  under  special  conditions. 

The  combustible  elements  in  these  fuels  are  carbon  and 
hydrogen,  the  former  burning  with  scarcely  any  visible  flame, 
and  the  latter  also  burning  with  a  colorless  flame.  The 
calorific  power  of  fuels,  that  is,  the  quantity  of  heat  evolved 
by  burning  one  gram  in  oxygen,  differs  greatly. 

The  unit,  in  terms  of  which  quantities  of  heat  are  meas- 
ured, is  the  calorie.  A  calorie  is  the  quantity  of  heat  re- 
quired to  raise  the  temperature  of  one  gram  of  water  one 
degree  centigrade.  Since  this  quantity  varies  with  the  tem- 
perature of  the  water,  it  is  usual  to  specify  that  the  water 
shall  be  at  15°  C.  and  be  raised  to  16°  C. 

The  Calorific  Power  of  some  combustibles  is  as  follows : l — 

Hydrogen,  to  liquid  water  .  34,462  Carbon,  to  CO .    .     .     .  2,473 

Marsh  Gas  (CH4).     .     .     .  13,063  Carbon  monoxid  (CO)   .  6,607 

Olefiant  Gas  (C2H4) .     .     .  11,868  Dry  Wood,  about .     .     .  3,664 

Sulfur 2,221  Coal,  about 7,600 

Wood  Charcoal,  to  C02      .  8,080 

As  many  combustibles  contain  some  oxygen  in  addition 
to  the  carbon  and  hydrogen,  in  order  to  find  the  actual 

1  Favre  and  Silbermann. 
23 


24  SANITARY   AND   APPLIED   CHEMISTRY 

amount  of  heat  developed,  we  estimate  what  would  be  pro- 
duced from  the  combustion  of  the  carbon,  and  of  so  much 
hydrogen  as  is  in  excess  of  that  necessary  to  form  water 
with  the  oxygen  present  in  the  fuel.  In  estimating  the 
available  heat  produced,  we  must  deduct  from  the  total 
calorific  power  the  amount  of  heat  necessary  to  convert 
into  steam  all  the  water  formed  by  the  combination  of 
the  hydrogen,  and  all  the  water  originally  present  in  the 
fuel. 

When  the  carbon  is  burned,  the  sole  pro/duct  of  the  com- 
bustion is  carbon  dioxid,  thus,  C  +  02  =  C02 ;  but  if  the 
combustion  is  incomplete  from  lack  of  sufficient  air,  the 
combustion  would  be  represented  also  by  the  equation, 
2  C  +  02  =  2  CO,  in  which  the  poisonous  gas,  carbon  mo- 
noxid,  is  formed  at  the  same  time  as  the  carbon  dioxid.  It 
will  also  be  seen  from  the  above  table  that  much  less  heat 
results  from  the  burning  to  carbon  monoxid  than  when  the 
carbon  burns  completely  to  carbon  dioxid.  Smoke  consists 
largely  of  unburned  carbon,  which  might  have  been  burned 
completely  to  carbon  dioxid  if  the  conditions  for  combus- 
tion had  been  better. 

In  the  burning  of  hydrogen,  nothing  but  water,  in  the  form 
of  steam,  is  produced,  thus,  2  H2  -f  02  =  2  H20.  In  addition 
to  the  above  products  there  are  some  others  that  are  inci- 
dental, and  due  to  impurities  in  the  combustibles. 

The  original  basis  of  the  ordinary  fuels  is  cellulose 
(C6H10Oa)n,  which  is  found  in  a  very  pure  form  in  clean 
cotton  and  in  pure  filter  paper.  It  is  believed  by  geolo- 
gists that  not  only  peat,  but  also  the  different  kinds  of  coal, 
came  originally  from  vegetable  material.  In  the  case  of  peat 
the  amount  of  oxygen  and  hydrogen  have  not  been  so  com- 
pletely eliminated  by  the  combined  action  of  heat  and 
pressure  in  the  earth,  as  in  the  case  of  the  soft  coals  and 
anthracite. 


FUELS  25 

•WOOD  AS  FUEL 

If  a  fuel  is  porous,  like  wood,  so  that  the  air  can  penetrate 
into  the  interior,  it  will  be  readily  ignited  and  burn  quite 
freely.  The  ordinary  practice  of  piling  the  wood  loosely  to 
build  a  fire  is,  of  course,  in  accordance  with  this  principle. 
If  the  fuel  contains  considerable  hydrogen,  especially  when 
united  with  oxygen,  as  is  the  case  with  wood,  it  is  free 
burning.  When  but  little  luminous  gas  can  be  formed,  as 
in  the  burning  of  charcoal,  coke,  or  anthracite,  the  heat  is 
more  intense  and  concentrated  at  a  point  near  the  burning 
material.  Other  fuels,  such  as  wood,  soft  coal,  petroleum, 
etc.,  burn  with  a  long,  smoky  flame,  and  the  heat  will  be 
distributed  over  a  larger  flue  surface. 

The  experience  of  foresters,  both  in  this  country  and  in 
Europe,  has  shown  that  to  be  fit  for  fuel  and  economical  for 
use,  the  softer  woods  must  grow  from  twenty  to  thirty  years 
and  the  harder  woods  from  fifty  to  one  hundred  and  twenty 
years.  In  many  parts  of  Europe  the  government  requires 
that  the  forests  be  renewed  as  often  as  they  are  cut,  and 
only  in  this  way  is  it  possible  to  keep  the  supply  of  fuel 
and  timber  intact.  The  preservation  of  forests  also  tends 
to  keep  the  moisture  in  the  soil,  so  that  the  streams  shall 
not  dry  up  in  summer  and  there  will  not  be  the  liability  to 
sudden  floods  that  there  is  in  regions  from  which  the  tim- 
ber has  been  cut. 

There  is  more  water  in  wood  that  is  cut  in  the  spring  than 
if  it  is  cut  in  January,  and  there  is  more  in  the  young  twigs 
and  stems  than  in  older  wood.  Different  varieties  of  freshly 
cut  wood  contain  the  following  per  cent  of  water :  — 

Willow 26.0%  Aspen 43.7% 

Sycamore 27.0%  Elm 44.5% 

Birch 30.8%  Fir 45.2% 

Oak 34.7%  Larch 48.6% 

Pine 39.7%  White  Poplar    ....  60.6% 

Beech 30.7% 


26  SANITARY   AND   APPLIED   CHEMISTRY 

One  and  a  half  to  two  years  after  being  cut  wood  gets  as 
dry  as  it  can  by  simple  exposure  to  the  air,  and  it  is  called 
"  seasoned  "  or  "  air  dried,"  but  it  still  contains  from  20  % 
to  25  %  of  moisture. 

Wood  several  years  old,  kept  in  a  warm  room,  may  still 
retain  17  %  of  moisture.  Wood  may  be  kiln-dried,  and  in 
this  process  will  lose  from  16%  to  20%  of  moisture.  If 
the  air  is  expelled  from  wood,  it  is  sensibly  heavier  than 
water,  and  the  specific  gravity  is  from  1.30  to  1.50.  On  ac- 
count of  being  heavier  than  water,  "  water-soaked"  wood,  or 
that  in  which  all  the  air  has  been  replaced  by  water,  will  of 
course  sink  to  the  bottom  of  a  stream. 

The  amount  of  moisture  in  wood  is  of  great  importance, 
because  of  the  large  amount  of  heat  that  is  used  up  in  its 
evaporation  when  burning;  and  so  it  goes  without  saying 
that  dry  wood  is  more  economical  than  green  wood.  Resin- 
ous woods,  such  as  fir,  spruce,  and  pine,  have  an  increased 
heating  value  on  account  of  the  pitch  and  resinous  gums 
which  they  contain. 

The  amount  of  ash  in  wood  differs  greatly  as  it  is  made 
from  old  or  young  wood  and  from  the  whole  wood  or  the 
bark.  Willow  wood  contains  2%  of  ash;  oak,  1.65%  ;  beech, 
1.06  %  ;  Scotch  fir,  1.04  %  ;  birch,  0.85%.  This  ash  consists 
essentially  of  sodium  and  potassium  carbonates,  calcium 
and  magnesium  carbonates,  with  some  phosphates,  sulfates, 
and  silica  (see  Soap,  p.  96). 

CHARCOAL 

When  wood  is  heated  in  a  limited  supply  of  air,  a  kind  of 
distillation  takes  place,  and  the  residue  that  is  left  is  called 
charcoal.  The  ordinary  method  of  charcoal  making  has 
been  to  pile  the  wood  and  cover  with  turf  or  soil,  and  then 
apply  a  flame  to  the  center  of  the  pile  and  allow  a  little  air 


FUELS  27 

to  enter  the  bottom  so  that  the  combustion  shall  go  on  slowly. 
This  process  requires  several  weeks,  and  no  attempt  is  made 
to  utilize  the  smoke  and  gas  given  off. 

Charring  in  kilns  has  more  recently  been  resorted  to,  and 
here  the  products  of  combustion  are  utilized.  The  wood  is 
placed  in  a  brick  kiln,  which  is  heated  by  the  combustible 
gases  given  off  from  other  furnaces  of  the  same  battery. 
The  smoke  and  other  products  of  combustion  are  drawn  out 
of  the  kiln  by  fans,  through  a  series  of  condensers,  where  the 
wood  alcohol,  tar,  and  crude  acetic  acid  are  deposited,  and 
afterward  purified  for  the  market.  About  27%  of  charcoal 
is  the  yield,  by  this  process,  while  only  20  %  is  produced  by 
the  charcoal  pit  process. 

PEAT 

This  fuel  is  very  slowly  formed,  especially  in  shallow 
pools,  by  the  decomposition  of  vegetable  matter.  The  peas- 
ants in  Great  Britain,  Northern  Germany,  Holland,  and 
some  other  countries  cut  the  peat  or  "  turf,"  as  it  is  some- 
times called,  into  cubical  blocks  and  pile  it  up  on  platforms 
to  dry.  As  it  often  contains  as  much  as  45  %  of  water,  it  is 
important  that  the  drying  should  be  thoroughly  done,  or  in 
burning  but  little  heat  will  be  obtained.  It  is,  of  course,  a 
cheap  fuel  and  burns  with  a  smoky  flame. 

A  peat  bog  is  composed  of  the  various  mosses  and  sedges 
that  grow  so  readily  in  damp  ground  and  die  at  the  end  of 
the  season,  to  be  succeeded  by  similar  vegetation  the  next 
season.  Sometimes  trunks  of  trees  are  found  in  it  and  even 
animal  remains.  Peat  has  about  the  following  composition : 
water,  16.4 ;  fixed  carbon,  41  % . 

It  is  estimated  that  there  are  in  Great  Britain  6,000,000 
acres  of  peat  swamps,  and  that  each  acre  would  yield  1000 
tons  of  peat  charcoal.  In  Ireland  one  seventh  of  the  whole 
island,  or  2,830,000  acres,  is  peat  bog.  The  value  of  peat 


28  SANITARY   AND   APPLIED   CHEMISTRY 

depends  on  its  dryness,  density,  and  firmness.    Peat  leaves 
from  8  %  to  12  %  of  ash. 

COAL 

Lignite  or  brown  coal  is  intermediate  between  peat  and 
ordinary  soft  coal  in  composition,  and  is  of  more  recent  for- 
mation than  the  latter.  Although  it  burns  freely,  it  contains 
from  15  %  to  20  %  of  moisture,  and  leaves  quite  a  large 
amount  of  ash. 

Cannel  coal  is  a  peculiar  variety  of  coal,  having  a  con- 
choidal  fracture  like  broken  glass,  and  only  a  slight  luster. 
The  name  comes  from  the  Scotch  pronunciation  of  the 
word  "  candle,"  and  refers  to  the  fact  that  splinters  of  this 
coal  will  burn  like  a  candle.  Cannel  coal  is  especially  valu- 
able for  making  illuminating  gas,  as  it  yields  a  large  quan- 
tity per  ton. 

Bituminous  coal  is  very  widely  distributed  in  most  coun- 
tries of  the  world.  Some  of  these  coals  burn  with  a  smoky 
flame,  and  "  cake,"  or  form  a  coke  which  is  hard  and  seems 
to  fuse  together,  while  others  are  "  non-caking,"  and  burn 
freely,  with  little  smoke,  to  an  ash.  The  latter  are  well 
adapted  for  domestic  use. 

In  the  use  of  an  oven  that  is  heated  with  a  fire  on  the 
outside,  this  is  a  cheap  and  satisfactory  fuel,  except  for  the 
abundance  of  smoke  which  it  gives  off. 

Semibituminous  coals  are  found  in  several  localities,  but 
particularly  from  Pennsylvania  across  the  southern  bound- 
ary of  Virginia  into  Tennessee.  The  volatile  matter  ranges 
from  12%  to  25%,  and  this  combustible  portion  is  quite 
uniform  in  composition. 

The  semianthracite  coals,  like  the  Eureka  and  Ouita  of 
Arkansas,  burn  freely,  with  but  little  flame,  and  show  a  ten- 
dency to  decrepitate  and  fall  through  the  grate. 

Anthracite  coal  occurs  only  in  a  few  localities,  but  often 


FUELS 


29 


in  very  thick  veins.  It  has  a  high  luster,  and  a  specific 
gravity  of  about  1.75.  It  burns  with  little  flame  and 
smoke,  and  is  admirably  adapted  for  domestic  use,  as  the 
heat  is  concentrated  and  intense  directly  over  the  fire 
rather  than  distributed  through  a  long  flue  as  when  soft  coal 
burns.  When  a  naked  fire  is  used  for  baking,  as  in  a  large 
cracker  bakery,  anthracite  or  coke  is  a  very  satisfactory  fuel. 
Coke,  the  material  left  in  the  retort  after  gas  has  been 
made  from  soft  coal  (  see  p.  54 ),  is  quite  a  bulky  fuel, 
and  leaves  considerable  ash.  It  is  also  made  in  "  beehive  " 
coke  ovens,  and  the  distillation  products  are  allowed  to 
escape. 

ANALYSIS  OF  VARIOUS  COALS 


VOLATILE  AND 

WATER 

COMBUSTIBLE 

ASH 

MATTERS 

CARBON 

Lignite  

1800 

20.90 

50.90 

10.20 

Seraibituminous,  Pa.1 

0.81 

21.10 

74.08 

3.36 

Bituminous,  Pa.1     .     .     . 

1.97 

38.60 

54.15 

4.10 

undet. 

37.20 

61.60 

1.20 

Canon  City,  Colo.    .    .    . 

6.47 

38.82 

49.10 

5.61 

Semianthracite,  Ark.  .    . 

1.11 

12.73 

77.62 

8.56 

Anthracite  i    

3.09 

4.28 

83.81 

8.18 

The  greater  the  amount  of  moisture  the  less  valuable  the 
fuel,  as  in  the  case  of  wood  mentioned  above.  The  "  vola- 
tile and  combustible  "  matter  referred  to  in  the  table,  is  that 
which  goes  off  when  the  coal  is  heated  in  a  closed  vessel.  It 
is  this  which  gives  the  smoky  flame  to  bituminous  coal. 
Fixed  carbon  is  the  coke,  which  finally  burns  with  little 
flame  and  leaves  a  residue  of  ash.  It  will  be  noticed  that 
there  is  a  regular  decrease  in  volatile  matter,  from  the  bitu- 
minous coal  to  the  anthracite,  and  a  corresponding  increase 

in  fixed  carbon. 

1  Trans.  A.  I.  M.  E. 


30  SANITARY   AND   APPLIED   CHEMISTRY 

Experiment  17.  Heat  about  2  g.  of  pulverized  bitumi- 
nous coal  in  a  platinum  or  porcelain  crucible  closely  covered, 
as  long  as  any  smoke  is  given  off.  When  the  cover  is  re- 
moved, the  mass  of  coke  will  be  found  in  the  crucible.  This, 
less  the  ash  which  would  remain  on  complete  combustion, 
constitutes  the  "  fixed  carbon  "  referred  to  above. 

In  many  localities  where  there  is  no  local  supply  of  coal, 
there  is  a  direct  relation  between  the  retail  cost  of  different 
kinds  of  coal  and  the  amount  of  fixed  carbon  which  they 
contain,  —  the  greater  the  per  cent  of  fixed  carbon  the 
higher  the  price. 

Experiment  18.  Compare  the  retail  price  of  different 
kinds  of  coal,  as  anthracite,  semianthracite,  bituminous, 
etc.,  and  the  composition  as  given  on  page  29. 

Natural  and  artificial  gas  are  both  important  fuels,  even 
for  domestic  use.  Natural  gas  has  been  in  use  on  a  small 
scale  for  a  number  of  years,  but  it  was  not  until  about  1880 
that  it  became  of  commercial  importance  in  the  United 
States.  It  is  now  obtained  in  quite  large  quantities  in 
Pennsylvania,  New  York,  West  Virginia,  Ohio,  Indiana, 
Kentucky,  Texas,  and  Kansas.  The  method  of  boring  the 
well  is  to  use  what  is  called  a  churn  drill,  which  pulverizes 
the  rock,  and  the  borings  may  then  be  washed  out  with  a 
stream  of  water. 

The  hole,  which  is  from  4  to  6  in.  in  diameter,  is  usually 
cased  with  iron  pipe  as  the  drilling  progresses,  but  the  cas- 
ing is  smaller  nearer  the  bottom.  The  depth  is  usually  from 
300  to  1600  feet.  The  gas  occurs  in  what  is  called  a  "  gas 
sand,"  which  is  often  quite  thick.  The  pressure  of  the  gas 
is  frequently  from  300  to  400  Ib.  per  square  inch,  so  that 
it  is  with  great  difficulty  held  in  check.  The  gas  is  often 
conveyed  in  pipes  for  hundreds  of  miles,  and  finally,  by 
regulators,  the  pressure  is  reduced  for  domestic  consumption 


FUELS  31 

so  that  it  shall  be  burned  'at  from  4  to  8  inches  of  water 
pressure. 

A  cheap  fuel  gas  can  be  made  in  some  sections  at  a  low 
price,  and  will,  it  is  hoped,  supersede  the  use  of  coal  for 
cooking  and  heating  in  large  towns  and  cities  where  nat- 
ural gas  cannot  be  obtained.  The  advantages  of  burning 
gas  over  any  other  fuel  are  obvious,  for  it  is  immediately 
available  to  warm  a  house  or  cook  a  meal,  and  there  is  no 
waste  of  fuel,  when  the  occasion  for  its  use  is  past.  There 
is  no  dust,  ashes,  or  smoke,  and  the  products  of  combus- 
tion can  be  carried  out  of  the  room  by  a  very  small  pipe. 
These  products  should,  however,  always  be  removed,  for  if 
allowed  to  accumulate,  the  carbon  dioxid  and  other  gases 
make  the  air  of  the  room  decidedly  impure.  The  gas  stove 
does  not  heat  the  room  in  summer  as  does  a  coal  stove,  and 
it  is  a  perfectly  safe  fuel,  which  is  more  than  can  be  said  of 
gasoline  as  ordinarily  used. 

The  burners  used  in  heating  by  gas  are  all  made  on  the 
principle  of  the  Bunsen  burner.  The  proper  amount  of  air  is 
allowed  to  enter  at  the  bottom  of  the  tube  or,  in  the  large 
burners,  through  the  "mixer."  The  burner  that  is  put  into 
a  cook  stove,  for  instance,  can  be  made  of  a  piece  of  two- 
inch  gas  pipe  capped  at  one  end  and  having  three  rows  of 
small  holes  drilled  in  the  top  from  one  end  to  a  point  near 
'the  other.  The  "  mixer  "  is  screwed  on  at  the  end  through 
which  the  gas  is  admitted.  There  is  little  danger  in  the 
use  of  natural  gas  if  ordinary  precautions  are  taken.  There 
is,  of  course,  a  possibility  that  the  pressure  may  change  so 
that  the  gas  may  go  out  at  night,  but  this  is  not  often  the 
case  with  the  present  methods  of  regulating  the  supply.  It 
is  true  that  there  are  some  cases  of  suffocation  from  the 
careless  use  of  natural  gas,  but  it  is  not  as  poisonous  as  coal 
gas  or  "water  gas"  (see  Lighting,  p.  54). 

The  composition  of  natural  gas  from  different  localities  is 
as  follows :  — 


32 


SANITARY  AND   APPLIED   CHEMISTRY 


OHIO 

INDIANA 

KANSAS 

RUSSIA 

Carbon  dioxid    .... 

.3 
5 

.26 
45 

.44 
33 

.95 

92.6 

92.67 

95.28 

92.49 

3.5 

3.63 

3.28 

2.13 

Oxygen      

.3 

.36 

Hydrogen           .     . 

2.3 

2  35 

94 

Hydrogen  sulfid      .     .     . 
Olefiant  gas,  etc.     .     .     . 

.2 
.3 

.15 
.25 

.67 

4.11 

The  preparation  and  properties  of  illuminating  gas  are 
discussed  under  Lighting,  p.  53. 

Gasoline,  one  of  the  products  from  the  distillation  of 
petroleum,  which  is  so  extensively  used  as  a  fuel  for  cook- 
ing in  some  localities,  is  burned  in  stoves  so  constructed  that 
the  liquid  is  converted  into  vapor  by  the  heat  of  the  burner 
before  it  is  burned,  and  it  is  also  mixed  with  sufficient  air 
so  as  to  burn  completely  with  a  blue  flame,  which  does  not 
deposit  soot  on  the  cooking  utensils. 

The  chief  danger  in  the  use  of  gasoline  is  due  to  the  fact 
that  it  gives  off  a  volatile  vapor,  even  at  ordinary  tempera- 
ture. The  vapor  of  gasoline  is  not  only  extremely  com- 
bustible, but  when  mixed  with  a  certain  proportion  of  air  it 
is  highly  explosive.  Gasoline  stoves  are  usually  so  con- 
structed that  the  tank  which  holds  the  liquid  is  at  some 
distance  from  the  flame  and  it  should  never  be  filled  without 
first  putting  out  the  fire. 

Kerosene  is  often  used  as  a  fuel  for  heating  and  cooking. 
It  should  be  burned  in  stoves  of  special  construction,  and 
usually  from  a  large  flat  wick.  There  is  danger  of  smoking 
unless  the  wick  is  carefully  trimmed.  The  products  of  com- 
bustion should  always  be  carried  away  by  a  suitable  flue,  as 
they  are  both  disagreeable  and  injurious. 


CHAPTER   III 

HEATING  AND  VENTILATION 

HEATING 

THESE  two  subjects  are  so  intimately  associated  that  one 
cannot  be  considered  without  the  other,  and  one  system 
should  be  installed  at  the  same  time  as  the  other. 

The  common  methods  of  heating  are  through  — 

(1)  Direct  radiation. 

(2)  Indirect  radiation. 

(3)  Direct-indirect  radiation. 

The  means  of  obtaining  the  heat  are :  — 

By  the  fireplace  or  open  grate. 

By  stoves. 

By  hot-air  furnaces. 

By  steam  with  direct  radiation. 

By  steam  with  indirect  radiation. 

By  hot  water  with  direct  radiation. 

By  hot  water  with  indirect  radiation. 

By  electricity. 

Direct  radiation  includes  the  use  of  a  fireplace  or  open 
grate,  which,  however  satisfactory  it  is  in  the  way  of  ventila- 
tion and  for  imparting  cheerfulness  to  a  room,  is  not  an 
economical  method  of  heating,  because  it  wastes  from  75  % 
to  90  %  of  the  fuel.  The  fireplace,  where  only  the  radiant 
heat  was  utilized,  was  the  primitive  method  of  heating  dwell- 
ings when  fuel  was  not  expensive.  Many  devices  have  been 
D  33 


34  SANITARY  AND   APPLIED  CHEMISTRY 

proposed  for  making  the  fireplace  more  efficient.  Among 
them  may  be  mentioned  the  ventilating  grate,  in  which  air 
is  brought  from  outside  and  heated  by  passing  back  of 
the  fire  and  then  comes  into  the  room  through  gratings 
above  the  fireplace.  The  Franklin  stove,  when  placed  partly 
in  the  room,  was  an  illustration  of  heating  by  a  combination 
of  the  radiation  and  convection  methods.  One  of  the  chief 
reasons  why  people  take  cold  so  easily  is  that  they  work,  eat, 
and  sleep  in  rooms  that  are  heated  to  a  high  temperature, 
with  little  moisture,  and  where  no  attention  is  paid  to  ven- 
tilation. The  fireplace,  which  was  universally  used  less  than 
seventy-five  years  ago,  furnished  pure  air,  although  the  heat 
of  the  room  was  badly  distributed. 

Under  the  head  of  direct  radiation  may  also  be  included 
the  heating  by  stoves,  or  by  pipes  or  radiators  carrying 
steam  or  hot  water.  When  the  room  is  heated  by  a  stove, 
as  air  is  necessary  for  the  combustion  of  the  fuel,  and  there- 
fore is  removed  from  the  room  through  the  chimney,  an 
equivalent  amount  must  enter  the  rooms  through  the  cracks 
around  the  doors  and  windows.  This  affords  some  venti- 
lation, but  not  enough  for  rooms  in  which  a  number 
of  persons  are  assembled.  Direct  radiation  systems  are 
cheaper  in  construction  and,  with  the  exception  of  the  open 
grate  or  fireplace,  do  not  use  as  much  fuel  as  indirect 
systems. 

When  rooms  are  heated  by  a  stove,  there  is  no  reason  why 
air  cannot  be  brought  in  from  the  outside  beneath  the  stove, 
and  pass  over  it  to  become  heated,  and  then  into  the  room. 
By  this  means  fresh  air  will  find  its  way  into  a  room,  and 
there  is  little  difficulty  in  removing  air  from  a  room,  espe- 
cially if  it  is  warm  or  under  a  little  pressure. 

In  the  use  of  the  stove  for  heating,  it  should  be  large 
enough  to  thoroughly  heat  the  room,  even  in  the  coldest 
weather,  without  running  it  at  its  fullest  heating  capacity. 


HEATING   AND   VENTILATION  35 

It  is  not  economy  to  heat  a  room  with  a  small  radiating 
surface.  The  air  of  the  room  that  is  in  contact  with  this 
surface  becomes  overheated.  Stoves  heat  a  room  largely 
by  convection,  that  is,  by  heating  the  air  that  is  directly  in 
contact  with  the  stove,  and  when  this  becomes  heated,  it 
rises  and  gives  place  to  colder  air. 

The  openings  at  the  bottom  of  a  stove  or  furnace  should 
be  so  arranged  as  to  completely  shut  out  the  air  if  necessary, 
and  thus  control  the  fire.  This  is  much  safer  than  the  prac- 
tice of  shutting  the  damper  in  the  pipe  as  this  will  often 
drive  the  products  of  the  combustion  into  the  room;  this 
might  occur  during  the  night,  especially  if  the  wind  dies 
down,  and  the  suffocating  carbon  dioxid  and  sulfur  dioxid, 
as  well  as  the  more  dangerous  carbon  monoxid,  would  be 
driven  into  the  room.  When  sufficient  air  for  complete 
combustion  is  not  admitted  below  the  fire,  more  carbon 
monoxid  will  result,  and  the  full  heating  value  of  the  fuel 
will  not  be  obtained. 

Indirect  radiation  may  be  secured  in  the  simplest  way  by 
the  use  of  the  ordinary  hot-air  furnace.  Here  air  is  brought 
from  the  outside  and  passes  over  the  heated  surface  of  the 
iron,  and  is  then  admitted  to  the  room.  If,  in  addition  to 
this,  open  grates  or  fireplaces  are  used,  the  heating  is  nearly 
uniform  and  the  ventilation  is  satisfactory. 

If  a  building  is  heated  by  a  furnace,  great  care  should  be 
taken  that  the  air  that  comes  into  the  room  is  from  out  of 
doors  and  not  from  the  cellar.  The  danger  of  ground  air 
has  been  spoken  of  (p.  20),  and  this  danger  is  still  greater 
if  it  is  contaminated  with  the  gases  that  arise  from  decayed 
vegetables  in  the  cellar.  The  amount  of  air  coming  into  the 
furnace  can  be  regulated  if  it  is  brought  in  from  outside, 
and  an  excess,  or  more  of  the  cold  air  than  is  thoroughly 
heated,  can  be  avoided.  If  there  is  not  enough  air,  the  flues  of 
the  furnace  are  liable  to  become  overheated,  and  the  furnace 


36  SANITARY  AND  APPLIED   CHEMISTRY 

will  thus  be  damaged,  and  the  air  that  does  come  in  under 
these  conditions  will  also  be  liable  to  contain  carbon  monoxid 
(see  p.  13)  and  on  this  account  be  poisonous.  The  open- 
ing for  the  admission  of  fresh  air  should  be  so  arranged 
that  the  winds  will  not  seriously  affect  the  amount  of  air 
admitted. 

It  is  a  common  practice  to  take  the  air  from  the  living 
rooms  and  the  hall  of  the  dwelling  and  return  it  over  the 
furnace,  thus  using  the  same  air  over  and  over  again.  While 
this  is  no  doubt  economical,  as  far  as  expense  of  fuel  is  con- 
cerned, a  part  of  the  air  at  least  should  be  taken  from  out  of 
doors,  and  air  should  be  reheated  only  in  the  coldest  weather, 
and  for  warming  the  house  in  the  morning. 

There  should  always  be  some  arrangement  for  adding 
moisture  to  air  that  is  heated,  as  the  capacity  of  heated  air 
for  taking  up  moisture  is  greatly  increased ;  and  if  moisture 
is  not  supplied,  unpleasant  sensations  from  the  apparent 
dryness  of  the  air  are  produced  and  there  is  greater  liability 
to  take  cold.  Pans  of  water  are  placed  in  the  hot-air 
chamber  of  a  furnace  to  allow  the  moisture  to  evaporate 
and  mix  with  the  air  which  enters  the  room. 

In  the  use  of  steam  with  indirect  radiation,  it  is  conven- 
ient to  have  steam  coils  in  the  lower  part  of  the  building 
so  situated  that  fresh  air  can  pass  over  them,  and  then 
through  suitable  flues  into  the  rooms  above.  Here  again 
some  provision  can  be  made  to  keep  the  incoming  air  moist, 
by  placing  pans  of  water  upon  the  steam  coils. 

Steam  is  generally  used  under  a  pressure  below  twenty 
pounds  per  square  inch,  so  the  temperature  is  not  very  much 
above  100°  C.  (212°  F.),  or  "  exhaust "  steam  from  an  engine 
may  be  used.  In  some  systems  high  pressure-steam  is  em- 
ployed, and  in  this  case  the  temperature  of  the  radiators 
is  considerably  above  100°  C.  If  direct  radiation  is  used, 
one  disadvantage  of  this  method  of  heating  is  that  the  air 


HEATING   AND  VENTILATION  37 

in  the  room  is  dry.  In  order  to  obtain  heat  from  the  steam, 
it  must  be  condensed  in  the  radiator,  so  there  must  be  an 
opportunity  for  the  water  to  run  back  freely  to  the  boiler 
or  to  a  steam  trap. 

"Water  is  used  for  heating  on  account  of  its  great  capacity 
for  retaining  heat.  The  hot  water  can  be  carried  in  pipes 
to  some  distance  from  the  boiler,  give  up  its  heat,  and  then 
be  returned  by  another  series  of  pipes  to  the  boiler.  The 
water  in  the  system  may  be  under  pressure,  but  it  is  usually 
carried  in  an  open  system,  with  a  small  tank  at  the  top  of 
the  building,  which  is  filled  occasionally  to  supply  the  waste 
of  evaporation  or  leakage ;  and  vents  must  be  provided  to 
allow  the  air  that  is  dissolved  in  the  water  to  escape.  Under 
these  conditions  the  hot  water  from  the  boiler  in  the  cellar 
flows  upward  through  the  pipes  and  radiators  and  warms 
the  building,  and  the  heavier  cold  water  runs  back  to  the 
boiler  and  enters  at  the  bottom  through  another  set  of  pipes, 
and  the  heat  keeps  the  water  circulating.  It  should  be 
noted  that  the  difference  in  weight  between  the  column 
of  hot  water  and  that  of  cold  water  is  what  keeps  up  the 
circulation  in  the  system. 

The  hot-water  system  has  this  advantage  over  steam  that 
as  soon  as  the  water  is  warm  enough  to  circulate  it  begins 
to  warm  the  room,  and  the  heat  is  retained  for  a  long  time 
after  the  fire  has  been  allowed  to  die  down.  In  the  case  of 
steam  there  is  no  heat  from  the  radiator  till  the  water  in  the 
boiler  is  above  the  boiling  point.  With  the  use  of  hot  water 
the  temperature  of  the  radiator  is  never  above  100°  C. 
and  usually  much  below  this,  and  with  a  suitable  surface 
for  evaporating  water  in  the  rooms  the  air  will  be  agreeable. 
As  the  temperature  of  the  radiating  surface  is  lower  than  in 
the  case  of  steam,  the  heating  surface  must  be  much  larger, 
and  so  it  is  more  expensive  to  install  a  hot-water  system. 
This  is  no  doubt  the  chief  reason  why  it  is  not  more 


38  SANITARY   AND   APPLIED   CHEMISTRY 

generally  used,  and  added  to  this  is  the  greater  liability  to 
leaks,  and  the  danger  from  freezing  if  not  handled  with  care. 

In  the  direct-indirect  method  of  heating,  air  is  brought 
from  the  outside  behind  or  below  a  steam  or  hot-water 
radiator  standing  in  the  room,  and  is  heated  in  its  passage 
over  the  radiator.  This  is  also  theoretically  very  satisfac- 
tory, as  good  ventilation  is  secured,  though  it  is  not  often 
attempted  on  a  large  scale. 

At  the  present  cost  of  electricity,  it  is  not  extensively 
used  for  heating,  except  in  the  case  of  street  cars  and 
small  offices.  With  the  increased  use  of  water  power  to 
produce  electricity,  the  use  of  this  heating  agent  will  no 
doubt  soon  be  much  more  common.  The  use  of  electrical 
cooking  devices  is  already  quite  large.  They  are  especially 
adapted  to  small  apartments,  or  rooms  where  there  is  extra 
danger  from  fire. 

VENTILATION 

But  little  attention  is  paid  to  ventilation  by  people  in 
general,  because  they  do  not  appreciate  the  injury  to  the 
body  as  it  is  so  gradual.  The  evil  effect  of  bad  air  can  be 
readily  shown  by  the  study  of  the  health  of  those  who  are 
confined  in  close,  badly  ventilated  barracks  or  tenements, 
or  of  workmen  in  crowded  factories.  Even  domestic  ani- 
mals thrive  much  better  in  light,  clean,  well-ventilated 
stables.  Consumption  in  some  form  is  the  result  of  living 
in  close,  badly  ventilated  rooms.  A  practical  demonstration 
of  the  fact  that  pure  air  is  inimical  to  the  growth  of  the 
bacilli  that  cause  consumption  is  shown  in  the  recent  methods 
of  treating  this  disease  by  requiring  patients  to  live  out  of 
doors  throughout  the  entire  year,  and  in  the  establishment 
of  sanatoria  in  elevated  regions,  where  an  abundance  of  fresh 
air  is  the  most  important  part  of  the  treatment. 

Many  public  buildings  have  no  provision  for  ventilation 


HEATING   AND   VENTILATION  39 

during  that  part  of  the  year  when  they  must  be  heated,  and 
this  is  the  case  even  with  those  buildings  that  are  intended 
to  accommodate  large  audiences.  There  is  a  great  want  of 
appreciation  of  the  necessity  for  ventilation,  so  that  house 
renters  never  think  of  making  any  inquiry  as  to  whether 
any  facilities  for  ventilation  exist  or  not.  In  many  schools 
and  assembly  rooms  there  is  no  provision  for  ventilation 
except  by  opening  windows  and  subjecting  the  audience  to 
a  dangerous  draft.  One  reason  for  this,  no  doubt,  is  that 
we  do  not  notice  that  air  is  impure  until  it  is  extremely 
impure.  We  suffer  great  discomfort,  especially  from  high 
temperature,  and  then  think  that  we  need  fresh  air. 

It  is  estimated  that  the  daily  respiration  of  each  indi- 
vidual is  346  cu.  ft.,1  and  the  amount  of  carbon  dioxid 
given  off  from  the  lungs  in  the  same  time  is  16.25  cu.  ft. 
It  might  seem  that  carbon  dioxid  that  is  produced  by  the 
combustion  of  oil  and  of  gas  and  in  the  process  of  respira- 
tion, since  it  is  heavier  than  the  air,  would  sink  to  the 
bottom  of  the  room,  and  remain  there ;  but  the  fact  is  that 
an  analysis  of  the  air  will  show  that  on  account  of  the  dif- 
fusion of  gases,  the  gas  in  question  will  be  nearly  uniformly 
distributed  throughout  the  room.  To  such  an  extent  is  this 
the  case  that  we  expect  to  find  greater  discomfort  in  the 
gallery  of  a  crowded  hall  than  on  the  first  floor,  since  the 
expired  air  being  warmer  tends  to  rise,  notwithstanding  its 
greater  content  of  carbon  dioxid  gas. 

The  air  of  overcrowded,  poorly  ventilated  rooms,  as  a 
result  of  life  processes,  is  altered  as  follows : 2— 

"  There  is  a  slight  diminution  in  the  amount  of  oxygen ; 
there  is  an  increase  in  the  amount  of  carbon  dioxid  along 
with  the  organic  pollution,  resulting  from  the  decomposition 
of  perspiration  and  epithelium  on  the  surface  of  the  body, 

1  J.  S.  Billings,  "Ventilation  and  Heating,"  p.  88. 
3  Ibid.,  p.  99. 


40  SANITARY   AND   APPLIED   CHEMISTRY 

and  from  gastric  and  intestinal  digestion  and  decomposi- 
tion; and  there  is  a  slight  elevation  of  temperature  and 
addition  of  moisture.  In  the  impure  air  there  are  more 
solid  particles  often  organic  upon  -which  may  be  deposited 
either  innocent  or  disease-producing  bacteria,  for  the  most 
part  the  former." 

A  prominent  author,1  in  speaking  of  this  "crowd  poison- 
ing," as  it  may  be  named,  calls  attention  to  the  fact  that  it 
induces  a  general  lowering  of  the  vital  processes,  impair- 
ment of  nutrition,  and  loss  of  muscular  strength ;  the  blood 
becomes  laden  with  effete  matters  from  diminished  aera- 
tion; a  craving  for  alcoholic  stimulants  follows  on  the 
nervous  depression;  and  the  subjects  of  this  poisoning  fall 
easy  victims  to  disease.  The  prevalence  of  "  consumption  " 
among  those  workmen  whose  time  is  passed  so  largely  in 
badly  ventilated  and  crowded  shops,  which  was  formerly 
charged  to  the  use  of  "  rebreathed  "  air,  is  now  believed  to 
be  only  remotely  chargeable  to  these  conditions;  for  they 
produce  lowered  vitality  and  less  resistance  to  infection  by 
spores  of  disease,  which  may  be  inhaled  with  the  dust, 
either  in  the  workrooms  or  elsewhere. 

Of  the  impurities  mentioned,  the  carbon  dioxid,  which  in 
moderate  quantities  is  not  poisonous,  is  the  most  readily 
determined  as  an  index  of  the  impurity  of  the  air,  so  special 
attention  is  given  to  this  substance  (see  p.  11). 

Another  source  of  contamination  in  a  living  room,  which 
should  not  be  neglected  when  the  room  is  artificially  lighted, 
is  the  products  from  the  combustion  of  illuminating  gas,  oil, 
or  candles.  This  not  only  decreases  the  per  cent  of  oxygen 
and  increases  the  per  cent  of  carbon  dioxid  in  the  air,  but 
it  introduces  other  gases,  such  as  sulfur  dioxid  and  ammo- 
nium compounds.  Ordinary  burners  use  from  3  to  6  cu.  ft. 
of  gas  per  hour,  and  so  in  a  large  room  there  would  be 

1  Willoughby,  "  Hygiene  for  Students,"  p.  166. 


HEATING  AND   VENTILATION  41 

required  from  1500  to  5000  cu.  ft.  of  air  per  hour  to  properly 
dilute  the  products  of  combustion. 

According  to  Parkes,1  the  amount  of  fresh  air  to  be  sup- 
plied in  health  during  repose  ought  to  be :  — 

For  adult  males,  3600  cu.  ft.  per  hour  for  each  person. 
For  adult  females,  3000  cu.  ft.  per  hour  for  each  person. 
For  children,  2000  cu.  ft.  per  hour  for  each  person. 

The  following  may  be  considered  as  a  conservative  esti- 
mate of  the  amount  of  air  required  in  buildings  of  ordinary 
construction : 2 — 

CUBIC  FEET  OP  AIK  PEE  HOUR 

Hospitals 3600  per  bed. 

Legislative  assembly  halls    ....  3600  per  seat. 

Barracks,  bedrooms,  and  workshops  .         .  3000  per  person. 

Schools  and  churches 2400  per  person. 

Theaters  and  audience  halls        .        .        .  2000  per  seat. 

Office  rooms 1800  per  person. 

Water  closets  and  bath  rooms     .        .        .  2400  each. 

Dining  rooms 1800  per  person. 

Those  who  are  taking  moderate  exercise  need  one  half 
more  air,  and  during  violent  exercise  three  times  as  much 
air  as  when  at  rest. 

These  amounts  are  much  larger  than  those  given  by 
Morrin,  the  French  writer,  but  in  view  of  the  contami- 
nation of  indoor  air  from  various  sources,  they  do  not  seem 
to  be  too  large.  In  the  Boston  Theater  50  cu.  ft.  per  minute 
per  capita  is  furnished.  Pettenkofer  says  the  amount 
of  air  should  be  from  23  to  28  cu.  ft.  per  minute.  Dr. 
Billings,3  an  authority  on  this  subject,  says  that  for  audience 
halls  30  cu.  ft.  of  air  is  necessary,  and  in  legislative  build- 
ings the  apparatus  should  be  such  that  at  least  45  cu.  ft 

*  "  Text  Book  of  Human  Physiology." 

2  J.  S.  Billings,  "Ventilation  and  Heating,"  p.  129. 

8  Loc.  cit.,  p.  128. 


42  SANITARY   AND   APPLIED   CHEMISTBY 

of  air  per  person  per  minute  can  be  furnished,  with  a  possi- 
bility of  increasing  to  60  cu.  ft.  At  the  Vienna  Opera 
House,  which  is  considered  one  of  the  best-ventilated  build- 
ings in  the  world,  15  cu.  ft.  of  air  per  minute  per  capita  is 
supplied. 

In  order  to  have  good  ventilation,  the  fresh  air  introduced 
into  the  room*must  be  ample  in  volume ;  it  must  be  free  from 
contamination  with  dust  and  germs.  It  must  be  warmed  in 
cold  weather,  and,  if  possible,  cooled  in  warm  weather,  and 
it  must  be  introduced  so  as  not  to  cause  a  draft.  There 
should  be  a  sufficient  quantity  of  air,  so  that  the  amount  of 
carbon  dioxid  in  the  air  at  any  time  shall  not  be  above  six 
parts  per  ten  thousand. 

The  ventilation  may  be  downward  or  upward,  and  both 
of  these  methods  have  their  advocates.  The  disadvantage 
of  upward  ventilation  is  that  the  heated  air  of  the  room  is 
carried  off  very  rapidly,  thus  increasing  largely  the  cost  of 
heating.  Greater  economy  of  heating  is  secured  by  drawing 
out  the  impure  air  from  a  point  near  the  bottom  of  the  room. 
If  drawn  off  at  the  top,  the  heat  does  not  diffuse  through- 
out the  room,  and  the  floor  is  liable  to  be  cold.  The  dis- 
advantage of  downward  ventilation  (that  is,  taking  the 
impure  air  out  at  the  bottom  of  the  room)  is  that  it  is 
sometimes  difficult  to  get  the  currents  of  air  to  move  in 
this  direction.  The  Chicago  Auditorium,  however,  is  ven- 
tilated in  this  way;  10,000,000  cu.  ft.  of  air  per  hour  is 
furnished,  with  a  velocity  of  1  ft.  per  second.  The  air  is 
changed  from  4£  to  5  times  per  hour.  This  result  is  brought 
about  by  the  use  of  four  blowers  to  force  air  into  the  room, 
and  three  exhaust  fans  to  take  it  out. 

In  general,  it  may  be  said  that  ventilation  may  be  accom- 
plished by  natural  draft  or  by  a  forced  draft.  The  air  may 
be  forced  into  a  room,  and  allowed  to  find  its  way  out  by 
flues,  or  it  may  be  allowed  to  find  its  way  into  the  room 


HEATING   AND   VENTILATION  43 

through  the  cracks,  and  be  taken  out  by  an  exhaust  fan. 
It  is,  however,  greater  economy  of  power  to  force  air  into 
a  room  than  to  draw  it  out  by  an  exhaust  fan.  In  some 
large  chemical  laboratories  the  tempered  air  is  blown  into 
the  room  by  means  of  a  fan,  and  then  is  carried  out 
with  a  good  draft  by  flues  connected  with  hoods  in  the 
walls. 

As  previously  intimated,  the  most  complete  systems  use 
both  pressure  blowers  and  exhaust  fans.  In  some  hospitals 
(and  in  these  buildings,  if  anywhere,  pure  air  is  necessary) 
the  air  is  introduced  through  a  perforated  cornice  at  the  top 
of  the  room,  and  is  then  drawn  out  a  short  distance  above 
the  floor  through  flues  which  are  ventilated  by  exhaust  fans. 

Where  there  is  no  other  way  of  securing  a  movement  of  a 
current  of  air,  it  is  possible  to  cause  the  air  to  rise  rapidly 
in  flues  at  the  side  of  the  room,  by  having  a  gas  jet  or  some 
source  of  heat  in  the  flue.  The  best  place  for  this  is  just 
above  the  openings  but  these  flues  should  be  much  larger  than 
those  usually  provided.  Systems  of  this  kind  that  work  with 
more  or  less  success,  have  been  in  use  in  school  buildings 
for  many  years.  In  this  case  a  fire  is  kept  burning  in  the 
furnace,  so  as  to  assist  in  the  removal  of  the  foul  air  from 
the  rooms  and  from  the  flues. 

When  the  pressure  blower  system  is  used,  the  air  is  drawn 
over  the  steam  pipes  in  the  winter  (see  p.  36),  and  it  may 
be  cooled  by  passing  over  refrigerating  pipes,  through  which 
cold  brine  is  circulated,  in  the  summer.  The  air  is  fre- 
quently sprayed  before  it  enters  the  room  to  remove  dust 
or  smoke,  or  the  dry  air  may  be  filtered  through  cotton  or 
cheese  cloth,  in  a  long  flue. 

If  large  halls  are  lighted  by  gas,  the  burners  should  be 
placed  outside  the  room,  thus  allowing  the  light  to  shine 
into  the  room  through  a  glass  dome.  This  avoids  heating 
the  room,  and  the  products  of  combustion  do  not  in  this  way 


44  SANITARY   AND   APPLIED  CHEMISTRY 

contaminate  the  air.  Much  of  the  foul  air  of  the  room 
will  escape  also  at  the  same  time  if  openings  are  left  in  the 
ceiling  near  the  place  where  the  gas  is  burned. 

Open  grates  may  be  used  in  connection  with  furnace  or 
radiator  heat  to  ventilate  the  ordinary  dwelling.  If  stoves 
are  used  in  closed  rooms,  cold  air  from  outside  may  be 
brought  in  below  the  stove,  allowed  to  pass  over  it,  and 
a  flue  may  be  provided  near  the  floor  for  the  escape  of  foul 
air  (see  p.  34). 

Various  other  devices  have  been  suggested  to  ventilate 
an  ordinary  room.  One  of  these  is  to  bore  gimlet  holes  in 
the  walls;  these  are  so  small  that  the  air  cannot  cause  a 
draft,  and  yet  they  will  admit  a  large  amount  of  fresh 
air.  An  excellent  plan,  and  one  that  can  be  easily  adopted 
in  any  schoolroom,  is  to  raise  the  lower  sash  and  place  a 
board  about  5  in.  wide  below  it,  and  then  air  will  be  admitted 
into  the  room  between  the  two  sashes  and  directed  upward,  so 
there  will  be  no  direct  currents.  One  disadvantage  of 
opening  the  windows  at  the  top  is  that  the  air  may  pass 
to  the  opposite  side  of  the  room,  so  those  persons  farthest 
away  from  the  window  will  feel  the  draft,  while  those  near 
by  will  not  notice  it. 

The  air  in  a  well- ventilated  room  should  be  in  motion, 
but  this  motion  should  not  be  over  3  or  4  ft.  per  second, 
for  otherwise  it  becomes  a  "  draft."  The  ordinary  dwelling 
fortunately  affords  numerous  openings  where  air  from  out- 
side can  enter,  if  the  air  within  the  room  is  removed  by  a 
chimney  or  a  heated  flue. 

Experiment  19.  Test  for  currents  of  air  in  a  room  by 
the  use  of  thistle  down  or  a  candle  flame. 

Experiment  20.  Test  the  temperature  at  the  top  and 
bottom  of  a  room,  and  in  different  localities. 


HEATING  AND   VENTILATION  45 

Experiment  21.  Test  for  the  moisture  in  both  a  cold  and 
a  -warm  room  by  the  use  of  the  hygrometer. 

Experiment  22.  A  "household  test"  for  air,  devised  by 
Angus  Smith,1  is  to  place  %  oz.  of  clear  limewater  in  a 
10£  oz.  bottle  containing  the  air  to  be  tested  for  carbon 
dioxid,  and  if,  on  shaking,  there  is  no  precipitate,  the  air 
contains  less  than  .06  %  of  this  gas,  and  is,  therefore,  fairly 
pure. 

See  Experiments  10  and  11  under  air. 

1  Kenwood,  "Public  Health  Laboratory  "Work,"  p.  203. 


CHAPTER  IV 
LIGHTING 

WE  may  properly  consider  that  there  are  two  kinds  of 
light,  natural  and  artificial.  The  most  common  methods  of 
obtaining  artificial  light  are  by  — 

(1)  Combustion. 

(2)  Chemical  action. 

(3)  Phosphorescence. 

(4)  Electricity. 

To  obtain  light,  the  body,  if  a  solid,  must  be  heated  to  incan- 
descence, or  if  a  gas  it  must  be  heated  till  it  glows.  A  carbon 
filament,  heated  to  incandescence  in  a  vacuum,  as  in  the  in- 
candescent electric  light,  is  a  familiar  instance  of  this  class 
of  illumination.  Again,  by  means  of  the  oxyhydrogen  blow- 
pipe, calcium  oxid  is  heated  to  a  white  heat;  and  when 
magnesium  is  burned,  the  intense  light  is  due  to  the  incan- 
descent magnesium  oxid.  When  charcoal  is  heated,  the  coal 
does  not  volatilize,  so  this  is  not  used  as  a  source  of  light, 
but  of  heat.  When  wood  is  heated,  although  the  wood  itself 
does  not  volatilize,  there  are  certain  volatile  hydrocarbons 
given  off,  and  these  have  the  property  of  becoming  incan- 
descent, or  the  carbon  in  them  does  so,  and  thus  light  is 
obtained  from  the  burning  wood. 

Ordinary  light-producing  substances  may  be  divided  into 
solid,  liquid,  and  gaseous.  It  is,  however,  the  gaseous  sub- 
stance in  either  case  that  burns  and  gives  the  light.  In  the 
solid  candle,  for  instance,  the  fat  of  the  candle  is  melted 

46 


LIGHTING  47 

by  the  heat  radiated  from  the  flame  and  becomes  a  liquid 
oil,  and  is  then  drawn  up  by  capillarity  into  the  wick, 
where  a  kind  of  distillation  takes  place  and  the  oil  is 
made  into  a  gas  which  will  burn.  When  any  oil  or  liquid 
substance  is  burned  in  a  lamp,  it  is  already  in  a  condition  to 
be  drawn  up  by  capillarity,  and  is  then  volatilized  as  before. 
Illuminating  gas  is,  however,  delivered  at  the  burner  in  a 
condition  to  be  burned  directly  without  any  previous  distil- 
lation, as  that  has  already  been  done  at  the  gas  works. 

The  ordinary  candle  flame  illustrates  very  well  the  theory 
of  combustion.  It  is  divided  into  three  zones  :  an  inner  zone 
of  unburned  gas ;  a  middle  zone,  where  partial  combustion 
takes  place ;  and  a  third  or  outer  zone  of  complete  combustion, 
where  there  is  very  little  light  but  much  heat.  It  is  in  the 
second  zone  that  the  illumination  takes  place ;  here  the  car- 
bon becomes  incandescent  or  white-hot.  The  products  of 
combustion  are  carbonic  anhydrid  and  water,  and  as  both 
these  gases  are  transparent,  they  do  not  prevent  the  light 
from  radiating  outward.  We  are  indebted  to  Michael  Faraday 
for  making  a  very  thorough  study  of  the  nature  of  flame 
as  long  ago  as  1835.  In  the  candle  flame  the  hottest  point 
is  at  the  end  of  the  inner  zone,  and  the  interior  of  the  flame 
is  unburned  gas. 

Experiment  23.  Press  down  into  a  candle  flame,  for  an 
instant  only,  a  sheet  of  white  paper,  and  notice  the  ring 
of  carbon  deposited  on  it.  In  a  similar  way  a  ring  of  car- 
bon may  be  deposited  on  a  piece  of  glass,  and  the  dark  center 
of  the  candle  can  be  seen  on  looking  down  inside  the  ring. 

Experiment  24.  Blow  out  the  flame  of  a  candle  that  is 
burning  with  a  long  wick,  and  after  an  instant  relight  the 
smoke  at  a  little  distance  from  the  end  of  the  wick.  The 
distillation  of  gas  proceeds  for  some  time  after  the  candle  is 
extinguished. 


48  SANITARY   AND   APPLIED   CHEMISTRY 

Ordinary  illuminating  gas  may  be  burned  in  the  bat-wing 
or  fish-tail  burner  to  produce  light ;  or  in  the  Bunsen  burner, 
where  there  is  enough  air  admitted  into  the  bottom  of  the 
burner  and  mixed  with  the  gas  to  give  complete  and  rapid 
combustion,  and  consequently  very  little  light. 

The  earliest  device  for  obtaining  light  was  perhaps  the  pine 
knot  or  the  torch,  and  this  was  followed  by  the  rushlight, 
and  the  link,  which  was  a  rope  saturated  with  pitch.  After 
this  came  a  crude  lamp  made  by  allowing  a  wick  to  fall  over 
the  edge  of  a  dish  containing  some  liquid  fat  and  then  a  lamp 
in  which  the  wick  came  through  the  hole  in  the  side  of  the 
vessel  or  in  the  lip.  There  are  many  very  beautiful  lamps 
of  these  types  found  in  ancient  ruins.  It  was  also  found 
possible  to  make  a  solid  light-giving  substance,  by  drawing  a 
piece  of  string  through  a  lump  of  fat,  and  later  this  was 
modified  by  casting  a  solid  fat  around  a  wick,  and  thus  the 
candle  came  into  use. 

CANDLES 

The  making  of  candles,  by  surrounding  thin  wicks  of  pith 
or  flax  with  tallow  or  wax,  dates  from  a  very  early  period. 
In  1313  they  are  mentioned  among  the  expenditures  of  the 
Earl  of  Lancaster.1  Molded  candles  were  introduced  into 
England  in  the  fifteenth  century. 

Candles  are  made  from  tallow,  stearin,  paraffin,  wax,  and 
spermaceti.  Although  tallow  has  been  in  use  for  a  long 
time,  there  are  serious  objections  to  it  because  the  fat  melts 
at  such  a  low  temperature  and  drips.  What  was  needed, 
then,  was  a  fat  that  had  a  higher  melting  point.  This  result 
was  obtained  by  using  a  mixture  of  fatty  acids  produced 
from  fats,  instead  of  using  tallow. 

Fats  and  oils  are  derived  from  both  the  vegetable  and 
animal  kingdoms.  They  are  really  compounds  of  organic 

1  Groves  and  Thorp,  "  Chemical  Technology,"  Vol.  II,  p.  6ft 


LIGHTING  49 

acids  with,  bodies  belonging  to  the  group  called  alcohols ; 
that  is,  they  are  glyceryl  salts  of  organic  acids,  mostly  of  the 
"fatty  acid"  group.  The  alcohol  is  usually  glycerol  or 
glycerin,  C8HS  (OH)8,  and  the  compounds  are  called  glycer- 
ides.  The  acids  most  commonly  found  in  these  glycerides 
are  stearic,  palmitic,  and  oleic.  Solid  fats  contain  more  of 
the  glyceryl  tri-stearate  or  "stearin"  and  the  glyceryl  tri- 
palmitate  called  "  palmitin."  The  liquid  fats  consist  largely 
of  the  glyceryl  tri-oleate  or  "olein."  (See  Soap,  p.  98.) 

Tallow  contains  75%  of  stearin  and  olive  oil  only  25%. 
One  of  the  best  products  used  in  candle  making  is  made  by 
heating  tallow  until  it  melts,  and  then  when  it  is  partially 
cold  putting  it  in  bags  in  piles  under  a  hydraulic  press  and 
squeezing  out  the  liquid  fat.  This  will  be  more  fully  dis- 
cussed under  Oleomargarine. 

There  are  several  methods  for  separating  the  fatty  acid 
from  glycerin.  This  may  be  done  by  the  use  of  steam, 
lime,  and  sulfuric  acid.  The  commonest  method  is  to 
heat  under  pressure  with  water,  and  a  small  percentage 
of  lime  or  zinc  oxid,  and  afterward  to  distill  with  steam. 
This  affords  the  two  products,  stearic  acid,  which  earlier  in 
the  process  is  separated  by  gravitation,  and  glycerin,  which 
is  carried  over  with  the  steam ;  both  of  these  are  market- 
able. The  stearic  acid  thus  produced  is  quite  crystalline, 
and  indeed  too  much  so  to  use  alone  in  the  manufacture  of 
candles.  In  actual  practice  it  is  mixed  with  a  little  paraffin 
to  prevent  crumbling. 

There  are  two  kinds  of  candles  in  use:  dipped  and 
molded.  To  make  the  former  the  wicks  are  dipped  and 
allowed  to  cool  and  then  repeatedly  dipped  again  till  the 
candle  is  large  enough.  A  more  modern  method  is  to 
pour  the  melted  fat  into  molds  in  which  wicks  have  been 
previously  suspended.  Many  attempts  have  been  made  to 
make  a  wick  that  will  burn  off  at  the  end  and  not  need 


50  SANITARY   AND   APPLIED   CHEMISTRY 

snuffing.  One  of  the  best  inventions  in  this  line  is  the  mak- 
ing of  one  thread  of  the  wick  shorter  than  the  rest  so  that 
it  will  pull  the  wick  over  to  one  side  where  it  is  burned  off. 
Paraffin  is  one  of  the  last  of  the  products  obtained  by 
the  distillation  of  petroleum.  (See  p.  52.)  Illuminating  oils 
and  lubricating  oils  distill  over  earlier  in  the  process. 
Paraffin  is  in  reality  a  mixture  of  hydrocarbons,  having  a 
high  boiling  point,  and  as  it  is  a  mixture  it  cannot  be  repre- 
sented by  a  formula. 

SPECIAL   ILLUMINATING  MATERIALS 

There  were  some  other  interesting  illuminating  materials 
in  use  in  the  United  States  between  the  40's  and  the  60's, 
before  kerosene  was  produced.  One  of  these  was  camphene, 
which  was  simply  refined  turpentine.  Another,  which  was 
intended  to  remedy  some  of  the  defects  of  camphene  and 
prevent  some  of  the  smokiness  of  the  flame,  was  called 
"  burning  fluid,"  and  was  a  mixture  of  turpentine  and  alco- 
hol. Various  fixed  oils,  such  as  lard,  whale,  olive,  colza, 
and  poppy-seed,  have  been  in  use  in  lamps  since  the 
earliest  times.  Before  the  discovery  and  utilization  of  Petro- 
leum an  oil,  known  as  "  coal  oil,"  was  obtained  by  the  distil- 
lation of  certain  coals,  and  a  "  shale  oil "  was  made  by  the 
destructive  distillation  of  bituminous  shales. 

KEROSENE 

Oil  was  first  found  in  Pennsylvania  in  1859  by  Colonel 
Drake. 

Kerosene  is  one  of  the  products  that  comes  off  in  the 
distillation  of  petroleum  or  rock  oil.  This  oil  is  obtained 
by  boring  to  a  depth  of  600  to  1800  feet,  and  is  frequently 
associated  with  natural  gas.  The  product  from  a  large  num- 
ber of  wells  is  carried  by  pipe  lines  hundreds  of  miles, 
even  through  a  mountainous  country,  to  a  refinery.  There 


LIGHTING  51 

are  more  than  3000  miles  of  these  pipe  lines  from  the  oil 
regions  of  Pennsylvania  and  adjoining  states  to  lake  or  sea 
ports.  A  barrel  of  oil  moves  forward  every  seven  seconds, 
or  at  each  stroke  of  the  pump  which  keeps  the  oil  moving. 
In  the  process  of  refining,  the  oil  is  heated  in  immense 
retorts,  and  the  more  volatile  products  are  distilled  and 
condensed  by  passing  through  pipes  surrounded  by  water. 
At  a  little  higher  temperature  another  product  is  given  off, 
and  another  at  a  still  higher,  till  at  last  a  residue  of  paraffin 
remains,  and  this  may  be  distilled  off  leaving  only  a  small 
amount  of  coke  in  the  retort.  Often  the  distillation  is  car- 
ried on  in  two  stages,  the  "  light  oils  "  being  first  distilled, 
and  then  the  "  heavy  oils  "  in  another  still. 

DISTILLATES   FROM  PENNSYLVANIA  PETROLEUM 

The  commercial  products  obtained  by  the  distillation  of 
crude  petroleum  have  various  trade  names,  but  the  generally 
accepted  classes  of  products  are  the  following,  beginning 
with  the  lightest:1  — 

1.  Cymogene,  which  is  gaseous  at  ordinary  temperatures. 
It  may  be  used  in  the  manufacture  of  artificial  ice. 

2.  Khigolene,  which  may  be  condensed  to  a  liquid  by 
the  use  of  ice  and  salt.     It  is  used  as  an  anaesthetic. 

3.  Petroleum  ether,  which  boils  from  40°  to  70°  C.     It 
is  used  as  a  solvent  for  caoutchouc. 

4.  Gasolene,  which  boils  from  70°  to  90°  C.     It  is  used 
as  fuel  and  in  gasolene  engines,  forming  an  explosive  mix- 
ture with  air. 

5.  Naphtha,  which  boils  at  80°  to  110°  C.     It  is  used 
in  vapor  lamps,  and  as  a  solvent  for  resins. 

6.  Ligroine,  which  boils  at  from  80°  to  120°  C.     It  is 
used  as  a  solvent. 

7.  Benzine,  which  boils  at  120°  to  150°  C.     It  is  used  as 
a  substitute  for  turpentine,  and  as  a  solvent. 

1  "Industrial  Organic  Chemistry,"  Sadtler,  p.  29. 


52  SANITARY  AND   APPLIED   CHEMISTRY 

8.  Kerosene  or  Burning  Oil,  which  is  graded  by  its  color 
and  "  fire  test."     It  has  a  flash  test  of  110°  to  150°  F. 

9.  Lubricating  oils,  which  have  a  gravity  of  from  32° 
to  38°  B. 

10.  Paraffin,  which  is  of  different  degrees  of  hardness, 
and  like  all  the  other  products  of  variable  composition.  It 
is  a  solid,  melting  at  from  51.°6  to  57.°3  C.,  and  is  used  in 
candle  making,  in  making  water-proof  papers,  chewing 
gums,  etc. 

The  crude  kerosene  is  purified  by  treatment  with  sul- 
furic  acid  and  alkali,  and  subsequently  by  bleaching,  in  tanks 
with  glass  roofs.  There  is  often  a  temptation  to  mix  the 
lighter  oils  with  the  heavier,  especially  when  the  former  are 
cheaper  and  there  is  not  so  much  use  for  them.  These  light 
oils,  however,  increase  the  danger  of  explosions  when  the  oil 
is  burned  in  a  lamp.  If  a  vapor  is  given  off  at  the  ordinary 
room  temperature  in  the  summer,  or  the  lamp  is  heated  so 
that  a  vapor  may  be  given  off  from  the  oil,  it  may  be 
mixed  with  air  in  such  proportions  that  an  explosion  will 
result.  The  following  grades  of  burning  oil  are  on  the 
market :  — 

110°  Fire  test  (Standard  white) 

120°     "        "     (Prime  white). 

150°    "        "    (Water  white). 

In  many  states  and  countries  laws  have  been  passed  fixing 
the  "  flash  point,"  or  the  "  fire  test,"  of  oils,  as  it  is  called. 
By  the  "  flash  point "  is  understood  the  temperature  at  which 
a  volatile  vapor  that  will  produce  an  explosion,  is  given  off. 
The  "  fire  test "  is  the  temperature  at  which  the  oil  will  take 
fire  and  continue  to  burn.  The  laws  of  Ohio  require  a  flash 
point  not  below  110°  F.  Those  of  New  York  require  a 
higher  point.  In  Kansas  the  requirement  is  the  same  as  in 
Ohio,  and  the  Foster  cup  is  designated  as  the  official  tester. 


LIGHTING  58 

A  simple  flash-point  apparatus  may  be  made  by  the  use 
of  a  small  beaker  filled  about  half  full  of  kerosene,  supported 
in  a  larger  beaker  or  vessel  containing  water.  The  oil 
may  be  heated  at  a  rate  not  faster  than  two  degrees  in  a 
minute.  Over  the  beaker  containing  the  kerosene  is  placed 
a  metallic  cover,  with  a  large  opening  in  it.  In  this  open- 
ing is  placed  a  thermometer,  with  the  bulb  in  the  kerosene. 
A  very  small  flame  is  applied  at  the  opening  above  the 
kerosene  from  time  to  time,  and  a  record  is  made  of  the 
temperature  at  which  the  slight  explosion  of  the  gas  ex- 
tinguishes the  flame.  This  is  the  flash  point. 

Experiment  25.  Pour  a  small  quantity  of  kerosene  into 
a  saucer,  and  touch  a  lighted  match  to  it.  The  oil  should 
not  be  ignited. 

Experiment  26.  Pour  about  2  cc.  of  gasolene  into  a  sau- 
cer, and  notice  how  readily  it  takes  fire,  and  the  smoky 
character  of  the  flame. 

Experiment  27.  Use  a  "  Foster  cup,"  or  some  convenient 
device  as  described  above,  for  testing  the  flash  point  of  sev- 
eral samples  of  kerosene.1 

ILLUMINATING  GAS 

Aside  from  natural  gas,  which  has  already  been  discussed 
under  fuels,  the  gas  used  for  lighting  is  either  coal  gas, 
water  gas,  air  gas,  Pintsch  gas,  or  acetylene  gas. 

Illuminating  gas,  known  as  coal  gas,  was  discovered  by 
Clayton  in  1664,  and  used  for  lighting  a  dwelling  in  Lon- 
don, by  William  Murdock,  in  1792.  It  did  not  come  into 
general  use,  however,  for  many  years,  for  London  was  not 
lighted  by  gas  till  1812,  and  Paris  in  1815. 

Gas  is  made  by  the  distillation  of  soft  coal  in  fire-clay 
retorts,  heated  to  a  cherry  red  by  a  fire  of  coke,  which  is 
1  B.  Kedwood,  "  Petroleum  and  its  Products,"  Vol.  II. 


64  SANITARY   AND   APPLIED   CHEMISTRY 

maintained  beneath  them.  In  addition  to  the  gas,  there  are 
several  by-products  made,  including  gas  carbon,  which  is 
found  attached  to  the  inside  of  the  retorts,  coke,  ammoniacal 
water,  and  coal  tar.  The  injurious  gaseous  constituents,  in- 
cluding the  sulfur  compounds,  are  removed  from  the  gas 
by  cooling,  washing,  and  passing  it  through  lime  purifiers, 
and  then  the  gas  is  stored  in  large  gas  holders,  for  distribu- 
tion through  the  city  mains.  A  ton  of  coal  will  yield  from 
8000  to  14,000  cu.  ft.  of  gas. 

The  gas  carbon  mentioned  above  is  used  in  making  elec- 
tric-light pencils  and  in  batteries.  The  ammoniacal  liquor  is 
used  for  the  manufacture  of  all  the  ammonia  compounds  of 
commerce.  The  coke  is  partly  burned  under  the  retorts, 
and  the  rest  is  sold  as  fuel,  and  finally  the  coal  tar  is  dis- 
tilled to  make  an  immense  variety  of  valuable  organic  sub- 
stances, including  many  photographic  developers,  the  aniline 
dyes,  carbolic  acid,  oil  of  wintergreen,  oil  of  "  mirbane,"  sali- 
cylic acid,  etc. 

Water  gas  is  made  by  passing  steam  over  incandescent 
coke  or  anthracite  coal.  This  gives  a  mixture  of  the  two 
gases,  hydrogen  and  carbon  monoxid,  thus :  — 

C  +  2H20=C02+2H2. 
C  +  C02  =  2CO 

These  gases,  however,  give  no  light,  and  so  the  gas  is  en- 
riched by  injecting  into  the  generator,  by  means  of  a  jet  of 
steam,  some  crude  petroleum,  which  at  the  high  tempera- 
ture breaks  up  into  volatile  hydrocarbons,  which  furnish 
light  when  burned.  On  account  of  economy  in  manufac- 
ture, this  gas  is  used  instead  of  coal  gas  in  many  American 
cities. 

Air  gas  was  much  used  for  lighting  detached  buildings 
before  electric-lighting  plants  could  be  so  reasonably  in- 
stalled. In  this  process  air  is  forced  through  vessels  con- 


LIGHTING  55 

taining  gasoline,  and  some  of  the  vapor  is  thus  carried  with 
the  air  into  the  pipes.  What  is  burned  then  is  really 
gasoline  vapor.  In  order  to  avoid  danger  from  fire,  the 
liquid  gasoline  is  stored  underground  outside  the  building. 

The  method  of  making  Pintsch  gas,  or  oil  gas,  was  in- 
vented in  1873,  and  it  has  found  great  favor  as  a  compressed 
gas  to  use  for  lighting  cars,  steamboats,  lighthouses,  and 
isolated  buildings.  It  is  made  from  crude  oil,  by  vapor- 
izing it  in  cast-iron  retorts.  The  oil  is  "  cracked "  in 
the  upper  chamber  of  the  apparatus,  and  the  vapor  is 
passed  into  the  lower  chamber  which  is  heated  nearly  to 
1000°  C.  to  "fix"  the  vapors  and  form  permanent  gases. 

Acetylene  gas  has  come  into  use  recently,  since  calcium 
carbid  (CaC2)  has  been  made  cheaply  in  the  electric  furnace 
by  the  use  of  powdered  coke  and  lime.  When  calcium  carbid 
is  treated  with  water,  acetylene  gas  is  produced  thus :  — 

CaC2  +  2  H20  =  Ca(OH)2  +  C2H2. 

This  gas  produces  a  very  brilliant  light,  as  there  is  much 
incandescent  carbon  in  the  flame.  A  burner  which  consumes 
only  half  a  foot  of  gas  per  hour  is  usually  the  most  efficient, 
especially  when  the  gas  is  burned  under  considerable  pres- 
sure. It  is  not  safe  to  compress  the  gas  to  more  than  two 
atmospheres,  as  an  explosion  is  liable  to  occur.  The  gas 
finds  considerable  use  in  country  houses,  on  yachts,  automo- 
biles, and  bicycles.  A  ton  of  calcium  carbid  of  80%  purity 
will  produce  10,000  cu.  ft.  of  acetylene  gas.1 

Illuminating  gas  gives  the  best  results  when  burned  at  a 
water  pressure  of  not  over  1£  in.  If  the  pressure  is  too 
great  the  gas  "blows"  and  the  light  is  decreased.  The 
amount  of  gas  burned  in  an  ordinary  burner  is  from  2  to 
8  cu.  ft.  per  hour,  dependent  on  the  rating  or  size  of  the 

1  Thorp,  "  Outline  of  Industrial  Chemistry,"  p.  293. 


56 


SANITARY  AND   APPLIED   CHEMISTRY 


burner  and  the  pressure  of  the  gas.  A  comparison  of  the 
coal,  water,  oil,  and  natural  gas  may  be  made  by  inspection 
of  the  following  analyses :  — 


COAL 

WATER1 

(Carbureted) 

PlNTSCH  OB 

OIL* 

NATUBAL  GAS* 

Carbon  dioxid  .     . 
Olefiant  gas,  etc.  . 
Carbon  monoxid  . 
Marsh  gas    .     .     . 
Nitrogen  .... 
Oxygen   .... 
Hydrogen    .     .     . 
Ethane    .... 
Hydrogen  sulfid    . 

1.22 
5.30 
7.50 
38.11 

.22 
47.65 

3.00 
16.60 
26.10 
19.80 
2.40 

32.10 

45.00 

.25 

.36 
.41 
93.35 
3.41 
.39 
1.64 

.20 

38.80 
1.10 

14.60 

From  these  analyses  it  is  evident  that  water  gas,  if 
breathed,  would  be  the  most  liable  to  produce  death,  since 
it  contains  the  most  carbon  monoxid.  Natural  gas  contains 
less  than  coal  gas. 

Experiment  28.  Test  coal  gas  for  carbon  dioxid,  by  passing 
it  through  lime  water  contained  in  a  Woulff  bottle.  For  this 
purpose,  put  through  a  hole  in  one  cork  a  tube  bent  at  a  right 
angle,  with  one  limb  extending  to  the  bottom  of  the  bottle, 
and  through  a  hole  in  the  other  cork  a  tube  of  the  same  size, 
bent  at  a  right  angle,  and  passing  just  through  the  cork. 
Fill  the  bottle  half  full  of  lime  water,  allow  the  gas  to  bubble 
slowly  through  this,  and  light  the  gas  that  escapes.  After 
a  time,  dependent  on  the  amount  of  carbon  dioxid  in  the  gas, 
there  will  be  a  deposit  of  calcium  carbonate  in  the  bottle. 

Ca(OH)2  +  C03  =  CaCOs  +  H,0. 


1  Thorp,  "  Outline  of  Industrial  Chemistry,"  p.  294. 

a  Min.  Res.  of  U.  S.,  1893.    Dept.  Interior.    Anal.  Edw.  Orton. 


LIGHTING  57 

Experiment  29.  To  test  the  gas  for  hydrogen  sulfid, 
allow  a  slow  stream  to  pass  through  the  empty  Woulff  bottle 
arranged  as  above,  in  which  is  suspended  a  piece  of  filter 
paper  which  has  been  dipped  in  a  solution  of  lead  acetate. 
The  paper  will  turn  brown  or  black  after  a  time  on  account 
of  the  formation  of  lead  sulfid  on  the  paper. 

Experiment  30.  To  test  the  pressure  of  the  coal  gas  used, 
the  apparatus  mentioned  in  Experiment  29  may  be  used.  If 
the  bottle  is  small,  a  straight  tube  about  eight  inches  (20  cm.) 
long  may  be  put  in  to  take  the  place  of  the  longer  bent  tube. 
Fill  the  bottle  about  one  third  full  of  water.  Attach  the 
gas  to  the  shorter  tube,  and  measure  the  height  of  the  col- 
umn of  water  raised  by  the  pressure  of  the  gas. 

Experiment  31.  Learn  to  read  a  gas  or  water  meter.  The 
figures  on  the  dial  having  the  highest  number  are  read  first, 
and  in  case  a  pointer  is  very  nearly  upon  any  figure,  notice 
by  reference  to  the  next  lower  dial  whether  it  is  above  or 
below  that  figure,  and  read  accordingly. 

Experiment  32.  To  make  acetylene  gas,  put  a  small  quan- 
tity of  calcium  carbid  in  a  test  tube.  Place  this  in  a  rack 
or  a  test-tube  holder,  and  carefully  bring  into  the  tube  a 
few  drops  of  water.  The  gas  will  be  immediately  given  off 
and  may  be  lighted. 

Experiment  33.  To  make  an  acetylene  lamp  use  a  heavy 
16  oz.  flask  provided  with  a  cork  having  two  holes.  In  one 
of  these  holes  put  a  dropping  funnel,  with  the  tube  extend- 
ing nearly  to  the  bottom  of  the  flask,  in  the  other  hole  a  tube 
bent  at  a  right  angle.  Place  about  an  ounce  of  calcium 
carbid  in  the  flask,  and  allow  water  to  drop  on  it,  a  very  small 
quantity  at  a  time,  by  the  use  of  the  dropping  funnel.  Pass 
the  gas  evolved  through  another  flask  or  Woulff  bottle 
containing  some  lumps  of  calcium  carbid ;  this  will  dry  the 
evolved  gas.  In  one  tubulature  of  the  drying  bottle  put  a 


58  SANITARY   AND   APPLIED   CHEMISTRY 

straight  tube,  to  the  top  of  which  is  fitted,  by  a  short  rubber 
tube,  a  special  lava  tip  designed  for  burning  acetylene  gas 
which  uses  one  half  a  foot  of  gas  per  hour.  A  brilliant 
light  will  be  obtained. 

Experiment  34.  In  the  incomplete  composition  of  illumi- 
nating gas  small  quantities  of  acetylene  are  formed.  Study 
the  phenomenon  which  takes  place  when  a  Bunsen  burner 
"  strikes  back  "  and  burns  at  the  base. 

LAMPS   AND  BURNERS 

A  great  variety  of  devices  have  been  used  to  utilize  oils 
and  gas  and  get  the  greatest  possible  illuminating  value  from 
them.  With  a  lamp,  where  kerosene  or  some  oil  is  used  as 
the  combustible,  the  glass  chimney  came  into  use  to  increase 
the  draft,  and  prevent  smoking.  If  the  substance  burned  is 
rich  iu  carbon,  as  is  the  case  with  gasoline  (Experiment  26), 
this  is  particularly  necessary.  Another  device  to  attain  the 
same  end  that  has  been  used  in  lighthouses  is  the  use  of  a 
pump,  run  by  clockwork,  to  keep  the  wick,  especially  of  a 
large  lamp,  saturated  with  oil.  A  blower,  concealed  in  the 
base  of  the  lamp,  has  also  been  introduced,  to  avoid  the  use 
of  a  chimney. 

The  invention  of  the  Argand  lamp  in  1786,  which  was 
applied  both  to  oil  and  gas,  and  in  which  the  air  enters  the 
inside  of  the  circular  flame,  was  a  distinct  advance  in  illu- 
mination. The  student  lamp  is  of  this  type.  The  flat  flame 
of  the  gas  burner  is  obtained  either  in  the  "  bat-wing  "  tip  or 
the  "fish-tail"  burner.  In  the  former,  the  gas  comes  out 
through  a  lava  tip,  which  has  a  narrow  slit  in  the  top ;  in 
the  latter,  the  gas  comes  out  through  two  opposite  openings, 
usually  in  a  metallic  tip,  and  the  resultant  of  these  two  cur- 
rents of  gas  is  a  flat  flame,  at  a  right  angle  to  the  currents 
of  gas. 


LIGHTING  59 

INCANDESCENT   GAS   LIGHTS 

On  account  of  the  fact  that  much  of  the  gas  in  common 
use  is  of  low  candle  power,  and  yet  has  great  "  fuel  value," 
numerous  attempts  have  been  made  to  utilize  this  heat  to 
produce  light.  Passing  over  many  of  the  systems  in  use, 
the  most  practical  at  the  present  time  is  the  Welsbach  sys- 
tem. This  was  invented  by  C.  Auer  von  Welsbach  in  1885- 
1887.  This  lamp  consists  of  a  Bunsen  burner  over  which  is 
suspended  a  "  mantle "  of  the  oxids  of  such  rare  earths  as 
cerium,  lanthanum,  thorium,  yttrium,  or  zirconium.  A 
cylinder  of  cotton  is  soaked  in  the  nitrates  of  these  metals, 
and  one  end  is  gathered  into  a  ring.  After  it  has  been  dried 
the  cotton  is  burned  off,  and  the  oxids  are  worked  into 
shape  upon  a  form.  Then,  in  order  to  preserve  this  fragile 
material,  it  is  plunged  into  a  bath  of  collodion,  paraffin,  or 
some  similar  substance  which  stiffens  it.  This  latter  ma- 
terial is  burned  off  when  the  mantle  is  put  in  place  over  the 
Bunsen  burner.  The  "life"  of  these  mantles  is  from  500 
to  1000  hr.,  and  even  if  they  have  not  become  ruptured, 
after  a  time  their  candle  power  is  very  much  lowered.  In 
one  experiment  when  burning  2.5  cu.  ft.  of  gas  per  hour,  at 
one  inch  pressure,  25.6  candle-power  was  obtained  at  first, 
after  500  hr.  only  18  candle  power,  and  at  the  end  of  1000  hr. 
13.7  candle  power. 

This  kind  of  burner,  which  is  designed  to  utilize  the  heat 
of  the  gas,  produces  a  high  candle-power  light,  uses  a  mini- 
mum of  gas,  and  is  satisfactory  with  natural  gas,  water  gas 
that  has  not  been  carbureted,  or  any  gas  that  is  a  poor  light 
producer. 

Experiment  35.  To  show  the  principle  of  light  due  to  an 
incandescent  solid  burn  a  piece  of  magnesium  ribbon,  or, 
better  still,  heat  a  piece  of  calcium  oxid  in  the  flame  of  the 
oxyhydrogen  burner. 


60  SANITARY   AND   APPLIED   CHEMISTRY 

ELECTRIC   LIGHTS 

In  the  modern  method  of  lighting  by  electricity  the  com- 
mon systems  are  the  use  of  the  arc  light,  in  which  pencils 
of  gas  carbon  are  heated  by  the  electric  current ;  the  incan- 
descent, in  which  a  filament  of  carbon  contained  in  a  bulb 
from  which  the  air  has  been  fully  exhausted  is  heated  by 
the  passage  of  the  current ;  the  tantalum  lamp,  in  which  the 
metal  tantalum  is  used  as  the  incandescent  material;  the 
inclosed  arc ;  the  mercury  vapor  lamp ;  and  the  Nernst 
lamp.  In  most  of  these  some  highly  heated  solid  gives  out 
the  light. 

Most  of  the  lights  that  have  been  mentioned  are,  at  the 
best,  wasteful,  because  we  get  heat  and  comparatively  little 
light,  when  light  and  not  heat  is  desired.  A  recent  author 
says  that  99%  of  the  energy  of  the  candle  flame  and  50% 
of  that  of  the  electric  light  does  not  appear  as  light.  This 
energy  is  not  only  wasted,  but  as  it  appears  in  the  form  of 
heat,  it  is  often  a  source  of  great  inconvenience.  Experi- 
ments have  been  made  on  the  phenomenon  of  phospho- 
rescence, and  on  the  light  of  the  firefly,  that  show  how  much 
superior  this  is  to  any  light  devised  by  man.  There  seems 
to  be  no  reason  why  man  cannot  hope  to  perfect  some  system 
of  lighting  that  shall  be  as  economical,  and  this  is  no  doubt 
the  light  of  the  future. 


CHAPTER  V 

WATER 

As  water  is  so  essential  to  human  life,  it  is  evident  that  a 
study  of  its  occurrence  and  liability  to  contamination  may 
be  undertaken  with  great  profit.  It  is  composed  of  two 
simple  elements,  hydrogen  and  oxygen,  both  invisible  gases, 
and  the  purest  water  is,  of  course,  that  which  is  formed  by 
the  union  of  these  gases. 

Water,  when  it  is  condensed  in  the  clouds,  is  compara- 
tively pure,  and  as  it  falls  through  the  atmosphere  it  dis- 
solves certain  gases  that  are  present  in  the  air,  and  at  the 
same  time  washes  the  air  free  from  suspended  organic  and 
inorganic  dust.  We  are  familiar  with  practically  pure 
water  in  the  form  of  distilled  water,  which  is  odorless  and 
tasteless  but  to  many  is  not  agreeable  as  drinking  water, 
because  it  does  not  contain  the  dissolved  gases  of  the  atmos- 
phere nor  the  mineral  salts  to  which  they  are  accustomed. 
If  it  is  aerated  by  shaking  with  air  and  a  very  small  quan- 
tity of  salt  is  added,  it  becomes  much  more  agreeable  as  a 
beverage. 

Natural  waters  may  be  divided  into :  rain  water,  which 
we  collect  in  cisterns,  spring  water,  brook,  river,  lake,  well 
(both  shallow  and  artesian),  and,  finally,  sea  water.  There 
is  another  class  of  waters,  which  are  especially  interesting 
from  a  medicinal  standpoint,  viz.  mineral  waters. 

Cistern  water  may  be  collected  practically  pure,  if  it  falls 
on  a  metallic  or  slate  roof  which  is  washed  off  with  the  first 
water  of  a  rain,  allowing  this  to  waste.  A  well-painted 
shingle  roof  may  also  be  used  for  collecting  the  water  if 

61 


62  SANITARY   AND   APPLIED   CHEMISTRY 

sufficient  care  is  exercised  in  washing  the  roof.  The  water 
of  a  cistern  should  be  aerated  by  the  use  of  some  kind  of 
a  chain  or  bucket  pump  that  will  carry  air  into  the  water. 
This  may  be  used  as  an  auxiliary  means  of  obtaining  water 
from  the  cistern,  even  if  an  ordinary  suction  pump  is  used 
for  domestic  supply. 

Spring  water,  when  it  has  flowed  through  sandstone  or 
granite  in  an  unpopulated  region,  is  usually  pure  and  free 
from  mineral  matter.  In  limestone  countries,  however, 
spring  water  is  liable  to  become  loaded  with  the  mineral 
substances  of  the  rocks  and  soil  through  which  it  perco- 
lates; and  on  some  of  the  alkali  plains  it  becomes  very 
strongly  impregnated  with  mineral  matter.  There  is  a  con- 
stant tendency  for  the  mineral  matter  to  concentrate  in 
river  water,  and  these  waters,  which  contain  the  soluble 
materials  of  the  soil,  finally  accumulate  in  the  ocean.  Dilu- 
tion with  nearly  pure  surface  waters  often  prevents  river 
water  from  increasing  in  mineral  salts.  The  gases  of  the 
atmosphere,  especially  the  carbon  dioxid,  assist  very  mate- 
rially in  the  solution  of  some  of  the  rocks.  Spring  water 
may  also  contain  organic  matter  from  peat  swamps,  which 
usually  gives  it  a  brownish  color. 

River  water  partakes  of  the  character  of  the  springs  and 
brooks  which  feed  it,  and  it  is  also  liable  to  become  con- 
taminated from  refuse  and  sewage  which  is  poured  into 
it  from  inhabited  regions.  As  a  large  stream  is  so  often 
used  to  carry  off  the  "  waste  of  civilization,"  in  the  form 
of  sewage,  it  is  seldom,  in  a  well-populated  district,  that 
river  water  can  be  used  with  safety  as  a  source  of  supply 
without  some  preliminary  treatment  by  filtration. 

•The  water  of  the  Great  Lakes  would  be  of  the  very  best 
quality  were  it  not  for  the  fact  that  it  is  difficult  to  dispose 
of  the  sewage  of  the  cities  on  the  banks  without  contaminat- 
ing the  water  supply.  This  difficulty  has  been  partially 


WATER  63 

overcome,  in  many  instances,  by  tunneling  out  several  miles 
under  the  lake  to  an  "  intake  "  to  get  water  uncontaminated 
by  the  city  sewage.  In  the  case  of  Chicago,  by  pumping  the 
water  containing  the  sewage  through  a  drainage  canal  away 
from  the  lake  into  the  Illinois  river,  the  water  supply 
is  protected. 

The  water  of  wells  will  be  pure  or  impure  as  the  soil 
around  them  is  pure  or  contaminated.  Generally  speaking, 
the  water  of  bored  and  cased  wells  is  purer  than  that  of 
ordinary,  shallow,  dug  wells,  and  the  water  of  artesian  wells, 
especially  those  which  penetrate  the  earth  to  the  depth  of 
from  300  to  1000  ft.,  is  usually  better  than  that  from  shallow 
wells.  As  an  ordinary  well  is  but  a  hole  in  the  ground,  it 
naturally  collects  the  surface  impurities  in  the  vicinity,  and 
in  cities  and  large  towns  this  water  is  liable  to  be  very  im- 
pure. It  may  contain  mineral  salts,  but  the  most  dangerous 
impurities  are  of  an  organic  nature.  The  character  of  these 
organic  impurities  is  significant,  as  it  is  a  key  to  the  past 
history  of  the  water  and  often  reveals  the  fact  that  it  has 
percolated  through  soil  contaminated  with  sewage  or  the 
waste  material  from  cesspools. 

Although  the  water  of  wells  is  liable  to  be  impure  from 
cracks  in  the  soil  through  which  the  foul  water  of  drains  or 
cesspools  has  entered,  yet  a  commonly  neglected  source  of 
infection  is  the  surface  drainage  that  may  find  its  way  into 
the  well,  because  it  is  not  carefully  covered.  When  the 
water  is  pumped  out  and  allowed  to  fall  on  dirty  planks, 
where  chickens  and  other  animals  resort,  there  is  every 
opportunity  for  contamination.  The  same  remark  applies 
to  cisterns,  which  sometimes  receive  not  only  the  drainage 
of  the  soil,  but  of  the  dooryard  where  all  the  slops  from  the 
house  are  thrown. 

Artesian  well  water  is  usually  free  from  dangerous  or- 
ganic matter.  The  term  "  artesian,"  a  name  derived  from 


64  SANITARY   AND   APPLIED   CHEMISTRY 

the  province  of  Artois  in  France,  where  these  wells  were 
first  used,  applies  strictly  speaking  to  deep,  flowing  wells. 
In  the  United  States  there  is  a  large  area  in  northern 
Florida,  and  one  in  the  vicinity  of  Charleston,  South  Caro- 
lina, where  an  abundance  of  water  is  supplied  by  artesian 
wells.  In  the  city  of  Memphis,  Tennessee,  where  some 
years  ago  there  was  an  epidemic  of  yellow  fever,  great  pains 
has  been  taken  to  obtain  pure  artesian  water  from  deep 
wells.  The  analysis  of  this  water,  which  was  made  some 
years  ago  by  the  author,  showed  it  to  be  exceptionally  pure, 
and  the  health  of  the  city  has  been  very  much  improved 
since  its  introduction.  Some  artesian  wells  have  penetrated 
to  such  a  depth  or  through  such  strata,  that  the  water  be- 
comes impregnated  with  too  much  mineral  matter,  so  that  it 
cannot  be  used  for  domestic  purposes.  This  is  the  case, 
for  instance,  with  a  well  bored  at  St.  Louis  to  the  depth 
of  over  2000  ft.  for  supplying  a  brewery.  The  water  con- 
tained so  much  salt  that  it  could  not  be  used. 

MINERAL   WATERS 

Mineral  waters  are  those  which  contain  an  excess  of 
some  ordinary  ingredients,  or  small  quantities  of  some  rare 
ingredients,  and  which  on  this  account  are  used  as  remedial 
agents.  There  are  besides  these  certain  waters  on  the  market, 
known  as  "  table  waters,  "  which  are  simply  very  pure,  and 
are  recommended  by  physicians  because  they  may  be  taken 
in  large  quantities  and  will  not  affect  the  system  by  any 
minerals  which  they  contain. 

I.     MINERAL  SUBSTANCES  IN  WATER 

Some  of  the  mineral  substances  found  in  natural  waters 
and  in  mineral  waters  are  the  following :  sodium,  calcium, 
magnesium,  iron,  aluminum,  lithium,  and  potassium,  com- 


WATER  65 

bined  as  silicates,  sulfates,  chlorids,  carbonates,  and  some- 
times as  borates  and  arsenates.  Common  mineral  substances 
in  waters  may  be  tested  for  as  follows :  In  making  the  tests 
for  mineral  substance  in  water,  it  is  advisable  to  first  test 
the  water  supply  of  the  laboratory,  and  if  it  does  not  con- 
tain the  substance  tested  for,  then  use  a  strong  mineral  water 
of  known  composition,  like  Apollinaris,  Hunyadi-Janos,  or 
Congress  water. 

Experiment  36.  Test  for  calcium  in  water  that  does  not 
contain  much  iron  by  adding  to  it  some  ammonium  chlorid, 
ammonium  hydroxid,  and  ammonium  oxalate.  The  forma- 
tion of  a  white  precipitate  of  calcium  oxalate,  especially 
after  boiling,  indicates  the  presence  of  calcium. 

Experiment  37.  Test  for  magnesium  by  first  filtering  off 
the  calcium  oxalate,  if  any  is  precipitated  in  the  previous 
experiment,  and  adding  to  the  filtrate,  which  should  contain 
some  ammonium  chlorid  and  ammonium  hydroxid,  hydrogen 
sodium  phosphate.  The  formation  of  a  white  crystalline 
precipitate  of  ammonium  magnesium  phosphate,  especially 
upon  shaking,  indicates  the  presence  of  magnesium. 

Experiment  38.  Test  for  iron  as  a  ferric  compound  by 
adding  a  few  drops  of  hydrochloric  acid  and  some  potassium 
ferrocyanid.  The  formation  of  a  dark  blue  precipitate  (Prus- 
sian blue)  shows  the  presence  of  ferric  salts.  To  test  for 
ferrous  salts,  add  to  some  of  the  water  a  few  drops  of 
hydrochloric  acid  and  potassium  ferricyanid.  The  forma- 
tion of  a  blue  precipitate  indicates  the  presence  of  ferrous 
compounds. 

Experiment  38  a.  Another  excellent  test  for  ferric  com- 
pounds is  to  add  to  a  slightly  acidified  sample  of  the  water 
a  few  drops  of  potassium  sulfocyanate.  The  production  of 
a  red  color  indicates  iron. 


66  SANITARY   AND   APPLIED   CHEMISTRY 

Experiment  39.  Test  for  aluminum  by  adding  to  the  water 
a  few  drops  of  ammonium  chlorid  and  ammonium  hydroxid 
in  excess.  The  formation  of  a  white  flocculent  precipitate, 
especially  upon  warming  and  allowing  the  solution  to  stand, 
indicates  aluminum.  In  the  presence  of  a  considerable  quan- 
tity of  a  ferric  compound,  the  iron  will  be  thrown  down  as  a 
reddish  precipitate,  thus  obscuring  the  aluminum  hydroxid 
precipitate. 

Experiment  40.  To  test  for  lead  add  to  a  sample  of  water, 
acidified  with  hydrochloric  acid,  a  little  hydrogen  sulfid 
water.  The  formation  of  a  black  or  brownish  coloration 
will  indicate  lead. 

Experiment  41.  In  order  to  show  how  readily  water,  espe- 
cially when  pure,  attacks  lead,  scrape  a  piece  of  sheet  lead 
till  it  is  bright  and  clean.  Place  this  in  a  beaker  of  distilled 
water,  and  allow  to  stand  for  an  hour  or  more.  Remove  the 
lead  from  the  water  and  test  the  water  for  lead  by  the  use 
of  hydrogen  sulfid  water. 

Experiment  42.  Test  for  sulfates  by  acidifying  a  sample 
of  the  water  with  hydrochloric  acid,  and  adding  a  few  drops 
of  barium  chlorid.  The  formation  of  a  dense  white  precipi- 
tate of  barium  sulfate,  especially  after  boiling,  indicates  the 
presence  of  sulfates. 

Experiment  43.  To  test  for  chlorids,  add  a  few  drops  of 
nitric  acid  to  the  sample,  and  then  silver  nitrate.  The 
formation  of  a  white  precipitate  of  silver  chlorid  indicates 
chlorids. 

Experiment  44.  To  test  for  the  total  amount  of  mineral 
matter  in  the  water,  evaporate  from  100  cc.  to  200  cc.  in  a 
weighed  porcelain  or  platinum  dish  on  a  water  bath.  Dry 
the  residue  at  120°  C.,  and  weigh.  Calculate  the  weight  in 
terms  of  grams  per  liter.  (The  dish  can  be  weighed  on  the 
ordinary  horn-pan  balance.) 


WATER  67 

Experiment  45.  To  test  for  carbonates,  add  a  few  drops 
of  hydrochloric  acid  to  the  residue  obtained  in  the  previous 
experiment.  If  carbonates  are  •  present  there  will  be  an 
effervescence  on  account  of  the  escape  of  carbon  dioxid  gas. 
This  solution  may  then  be  tested  for  potassium  and  sodium 
by  dipping  into  it  a  platinum  wire,  which  is  heated  in  the 
Bunsen  burner  and  the  flame  can  be  examined  with  the 
spectroscope. 

Experiment  46.  To  test  for  sulfur  or  hydrogen  sulfid  in 
a  water  like  that  from  sulfur  springs,  plunge  a  silver  coin 
into  the  water,  and  in  the  presence  of  soluble  sulfids  it  will 
be  quickly  blackened  on  account  of  the  formation  of  silver 
sulfid,  Ag2S. 

HARD   WATERS 

Some  waters  contain  large  quantities  of  calcium,  magne- 
sium, iron,  and  aluminum.  Those  which  contain  these 
metals  associated  with  the  carbonate  radical  making  calcium 
acid  carbonate,  magnesium  acid  carbonate,  etc.,  are  called 
temporarily  hard  waters,  and  those  which  contain  calcium, 
magnesium,  iron,  or  aluminum  sulfates  or  chlorids,  are  called 
permanently  hard  waters.  This  distinction  is  made  because 
the  carbonate  waters  can  be  readily  softened  by  adding  to 
them  lime  water  in  sufficient  quantity,  while  it  is  much  more 
difficult  to  soften  the  permanently  hard  waters.  Another 
reason  for  this  distinction  is  that  a  considerable  quantity  of 
the  mineral  matter  is  precipitated  by  boiling,  in  accordance 
with  the  equation :  — 

CaH2  (C03)2  +  heat  =  CaC03  +  C02  +  H20. 

The  difference  between  the  hard  and  soft  water  may  be 
readily  shown  by  the  action  upon  the  two  varieties  of  a  soap 
solution. 

Hard  waters  produce  serious  inconvenience  when  used  in 
steam  boilers,  depositing  a  scale  of  greater  or  less  thickness, 


68 

which  causes  great  loss  of  fuel  by  interfering  with  the 
transmission  of  heat  to  the  water,  and  is  liable,  if  it  becomes 
thick  enough,  to  allow  the  iron  to  become  overheated,  and 
greatly  increase  the  tendency  to  explosion.  The  same  kind 
of  a  scale  is  often  found  in  a  tea  kettle  when  hard  water  is 
used.  There  is  an  immense  advantage  in  substituting  soft 
water  for  hard  when  the  item  of  soap  is  considered.  It  is 
estimated  that  in  Glasgow,  where  the  soft  water  of  Loch 
Katrine  was  substituted  for  hard  water,  there  was  a  saving 
in  soap  to  the  inhabitants  of  the  city  of  nearly  $200,000 
annually.  It  is  supposed  that  hard  waters  sometimes  cause 
diseases,  like  goiter.  There  are  some  districts  in  India 
where  10%  of  the  people  are  afflicted  with  this  disease, 
and  it  has  been  noticed  that  the  water  used  there  is  strongly 
calcareous.  Recent  investigations  by  Walters1  led  him  to 
believe  that  goiter  is  due  to  an  organism  of  the  amosba  type, 
found  in  the  water  rather  than  to  the  presence  of  mineral 
salts.  The  table  on  p.  73  shows  the  amount  of  mineral 
matter  (total  residue)  in  some  city  supplies  in  the  United 
States. 

Experiment  47.  Prepare  a  sample  of  very  hard  water  by 
adding  considerable  calcium  chlorid  to  a  sample  of  ordinary 
water,  and  pour  this  into  a  tall  cylinder.  Add  to  this  some 
soap  solution,2  shake  thoroughly,  and  notice  how  many  cubic 
centimeters  of  the  soap  solution  must  be  used  before  a  per- 
manent lather  is  produced  in  the  water.  Compare  this  with 
a  similar  experiment  made  with  soft  or  distilled  water.  No- 
tice also  the  abundant  precipitate  of  "  lime  soap  "  in  the  hard 
water. 

1  British  Medical  Journal,  1897. 

2  To  make  a  soap  solution  Mason  ("  Water  Supply,"  p.  360)  recom- 
mends to  use  10  g.  of  Castile  soap,  scraped  into  fine  shavings,  and 
dissolved  in  a  liter  of  alcohol  diluted  with  one  third  water.    Filter,  if 
not  clear,  and  keep  in  a  tightly  stoppered  bottle. 


WATER  69 

II.     ORGANIC  MATTER  IN  WATER 

The  mineral  constituents  of  water:  those  which  give 
character  to  the  so-called  mineral  waters,  which  make  water 
hard,  which  give  saltness  to  brine,  and  the  peculiar  charac- 
teristics to  the  "alkali"  waters  of  the  plains,  have  been  pre- 
viously discussed.  There  are,  however,  other  substances  in 
waters  which  it  may  not  be  possible  to  detect  there  either 
by  the  sense  of  taste,  smell,  or  sight,  and  yet  these  sub- 
stances, which  constitute  the  "  organic  matter,"  are  from  a 
sanitary  standpoint  of  the  greatest  importance. 

As  has  been  stated  the  mineral  matter  comes  from  the  de- 
composition of  the  rocks  and  of  the  soil  through  which  the 
water  percolates.  In  a  similar  way,  the  organic  material 
comes  from  the  soil  through  which  the  water  passes,  or  over 
which  it  runs.  It  is  difficult  to  tell  the  source  of  the  organic 
matter  from  a  simple  analysis  of  the  water.  It  may  come 
from  peat  swamps  in  which  decomposing  vegetable  matter 
has  remained  for  a  long  time  in  contact  with  the  water ;  it 
may  come  from  the  decayed  leaves  or  wood ;  or,  what  is 
much  worse,  it  may  be  from  decomposed  animal  matter, 
which  finds  its  way  into  a  stream  or  well  from  some  cesspool 
or  barnyard  or  foul  kitchen  drain. 

The  chemist  in  making  a  sanitary  analysis  of  a  water  deter- 
mines its  color,  odor,  and  turbidity,  as  well  as  the  residue 
left  on  evaporation,  loss  on  ignition  of  this  residue,  free 
ammonia,  albuminoid  ammonia,  nitrogen  present  in  nitrites, 
nitrogen  present  in  nitrates,  chlorin,  oxygen  consuming 
power,  and  hardness.  From  a  consideration  of  all  this 
data;  from  a  knowledge  of  the  locality  from  which  the 
water  comes  ;  from  comparisons  with  other  waters  from  the 
same  locality,  all  together  he  is  able  to  form  an  opinion 
as  to  whether  the  water  is  safe  for  domestic  use.  A  bac- 
teriological examination  will  also  be  of  value  in  estimating 
the  character  of  the  water. 


70  SANITARY   AND   APPLIED   CHEMISTRY 

The  ammonia  is  not  in  itself  injurious,  but  is  an  index  of 
nitrogenous  matter,  which  is  liable  to  be  dangerous.  "When- 
ever there  is  matter  of  this  kind,  bacteria  find  the  conditions 
suited  to  their  growth,  and  some  of  these  may  be  pathogenic 
in  character  and  so  are  liable  to  produce  disease. 

Free  ammonia  is  usually  considered  to  be  indicative  of 
recent  contamination,  especially  of  animal  origin,  while 
albuminoid  ammonia  indicates  more  especially  nitrogenous 
matter  that  has  not  undergone  sufficient  decomposition  for 
the  formation  of  ammonia  compounds.  If  the  water 
changes  in  its  ammonia  content  from  day  to  day,  this  also 
shows  that  it  is  in  a  dangerous  condition.  As  to  the  amount 
of  these  substances  which  may  be  allowed  in  a  good  water, 
it  is  practically  impossible  to  set  a  standard,  as  local  condi- 
tions are  so  variable.  What  would  be  a  fair  standard  for  a 
water  from  one  source,  would  not  apply  at  all  to  water  of 
a  different  character.  Professor  Mason  reports  an  excellent 
mountain  stream  as  containing  as  high  as  .055  parts  of  free 
ammonia  and  .230  of  albuminoid  ammonia  per  million. 
Professor  Mallet  reports  the  average  of  a  number  of  city 
supplies  considered  good  as  containing  .152  parts  of  albumi- 
noid ammonia,  and  Professor  Leeds  would  limit  the 
amounts  to  free  ammonia  .01  to  .12  per  million  and  albumi- 
noid ammonia  .10  to  .28  per  million. 

Free  ammonia  is  determined  in  a  water  by  distilling  a 
half  liter  and  testing  the  several  portions  of  50  cc.  of  the 
distillate  with  Nessler  solution.  The  brown  color  produced 
is  compared  with  that  obtained  in  solutions  of  ammonia  of 
known  composition.  When  the  free  ammonia  has  been 
distilled  off,  some  alkaline  permanganate  solution  is  added, 
and  the  ammonia  thus  set  free  on  distillation  is  determined 
as  before.  This  is  the  albuminoid  ammonia. 

The  nitrites  in  water  are  indicative  of  a  changing  con- 
dition of  oxidation,  which  is  completed  when  the  nitroge- 


WATER  71 

nous  bodies  are  changed  to  nitrates.  The  determination  of 
nitrates  is  considered  of  value  in  supplying  some  data  as  to 
the  previous  history  of  water.  If  the  nitrates  are  abundant 
this  indicates  that  at  some  earlier  stage  in  the  history  of  the 
water  it  may  have  been  contaminated  with  sewage,  and 
although  there  may  be  no  free  ammonia  present,  we  have 
no  proof  that  the  pathogenic  germs,  that  once  existed  in  the 
water,  are  destroyed  by  the  oxidation  which  the  ammonia 
has  undergone. 

In  regard  to  the  nitrates,  it  is  evident  that  there  must  be 
some  of  these  in  natural  waters,  for  both  nitrites  and  nitrates 
are  washed  out  of  the  air  and  carried  into  the  soil,  and  we 
depend  upon  the  nitrates  as  well  as  other  nitrogenous  com- 
pounds in  the  soil  to  assist  in  the  growth  of  plants.  The 
determination  of  nitrates  is  regarded  by  Mallet  as  of  great 
importance,  and  he  places  the  figures  for  the  amount  as 
averaging  0.42,  the  extreme  limit  being  1.04  parts  per  million. 
He  notices  that  waters  known  to  be  polluted  contain  sometimes 
from  7.239  to  28.403  parts  of  nitrogen  as  nitrates  per  million. 
The  average  for  American  rivers  is  given  as  from  1.11  to  3.89 
parts  per"  million,  and  the  author  has  found  in  city  wells 
from  14.5  to  30  parts  per  million  of  nitrogen  as  nitrates. 

The  Rivers  Pollution  Commission  (Eng.)  gives  the  follow- 
ing averages  from  589  unpolluted  waters  for  nitrogen  as 
nitrites  and  nitrates. 

PARTS  PEE  MILLION 

Rain  water 03 

Upland  surface      .        ...  .09 

Deep  well 4.95 

Spring 3.83 

In  some  localities  the  determination  of  chlorin  may  be  of 
value,  especially  where  the  normal  chlorin  content  of  the 
ground  water  is  known.  The  soil  of  several  of  the  New 
England  states  has  been  thoroughly  studied,  the  normal 


72  SANITARY  AND   APPLIED   CHEMISTRY 

amount  of  chlorin  for  each  locality  has  been  pretty  accu- 
rately determined,  and  a  map  has  been  prepared  showing 
where  equal  amounts  of  chlorin  are  found.  An  increase  in 
chlorin  would  show  probable  pollution  with  sewage.  In 
many  places,  however,  there  is  so  much  salt  in  the  soil  that 
the  determination  of  chlorin  is  of  no  value. 

Experiment  48.  To  make  Nessler's  solution,  dissolve  8  g. 
of  mercuric  chlorid,  HgCl2,  in  a  quarter  of  a  liter  of  pure 
water.  Dissolve  17  g.  of  potassium  iodid,  KI,  in  100  cc.  of 
pure  water.  Pour  the  first  solution  into  the  second  until  a 
slight  permanent  precipitate,  which  does  not  disappear  on 
shaking,  is  produced.  Add  80  g.  of  solid  potassium  hy- 
droxid,  KOH,  dilute  to  one  half  a  liter,  cool,  and  add  drop  by 
drop  some  of  the  mercuric  chlorid  solution  till  there  is  a 
slight  permanent  precipitate.  Allow  to  settle  for  some  time, 
and  pour  off  the  clear  yellowish  solution  for  use.  The  old 
"  Nessler  "  is  better  than*  one  which  is  recently  made. 

Experiment  49.  Test  a  sample  of  the  distilled  water  used 
in  the  laboratory  for  ammonia  by  placing  some  of  it  in  a  long 
test  tube,  or  a  so-called  Nessler  tube,  standing  on  a  piece  of 
white  paper,  and  adding  to  it  2  cc.  of  Nessler  solution. 
Notice  the  brown  tint  of  the  solution. 

Experiment  50.  Distill  about  500  cc.  of  well  or  river  water 
slowly  from  a  liter  retort,  condense  the  steam  in  a  flask  float- 
ing in  a  pan  of  water,  and  test  about  50  cc.  in  a  long  tube  by 
adding  2  cc.  of  Nessler  solution,  and  allowing  the  mixture  to 
stand  a  few  minutes.  Unless  the  water  is  very  pure,  there 
will  be  a  distinct  brown  coloration. 

Experiment  51.  To  test  for  nitrates  in  water,  add  to  about 
10  cc.  in  a  test  tube  an  equal  quantity  of  concentrated  sul- 
furic  acid  and  cool  the  solution.  Then  add  to  this  cau- 
tiously, without  mixing,  a  strong  solution  of  ferrous  sulfate. 
The  formation  of  a  brown  ring  where  the  two  liquids  come 


WATER 


73 


together  indicates  the  presence  of  nitrates.  This  test  is 
delicate  only  to  about  ten  parts  of  nitric  acid  in  a  million 
parts  of  water.  A  very  small  crystal  of  saltpeter,  potassium 
nitrate,  may  be  used  in  the  water  to  show  the  test. 

Experiment  52.  To  test  for  organic  matter  when  present  in 
large  quantity,  add  to  a  sample  of  water,  contained  in  a  tall 
stoppered  cylinder,  a  little  dilute  sulfuric  acid  and  a  few 
cubic  centimeters  of  a  1  %  solution  of  potassium  permanganate. 
The  purple  color  of  this  solution  is  discharged  by  shaking  with 
water  containing  organic  matter,  so  the  amount  of  organic 
matter  may  be  estimated  relatively  by  noticing  how  much 
permanganate  must  be  used  to  produce  a  permanent  purple 
color  in  the  water.  (This  same  reagent  may  be  used  prac- 
tically on  a  large  scale  to  remove  the  foul  odor  of  cistern 
water.  Potassium  permanganate  should  be  added  to  the 
water  until,  on  mixing,  there  is  a  slight  pink  tint  to  the 
water.) 

ANALYSIS  OF  CITY  WATER  SUPPLY  * 
(PARTS  PER  MILLION) 


6 

i 

a 

ss 

,1 

, 

g 

1 

a  < 

z  z 

3 

^   K 

S-  W 

£  H 

S3g 

a 

N 

§ 

o  5 

"  « 

O>  X 

1 

*<•< 

o 

j^ 

^.  H 

.So 

g 

£ 

<1 

E-i 

Springfield  Mass    Aver   1893  

.009 

.204 

1  50 

.001 

.026 

5  132 

37  6 

Boston              "        "       1894  

.006 

319 

410 

.001 

.106 

6.295 

464 

035 

.140 

0  70 

0 

1  525 

70  0 

050 

.125 

450 

2  287 

85  0 

Rock  Island    111   (Miss.  E  )  

.025 

.260 

1.00 

0 

trace 

6  000 

1400 

New  Orleans  La  (Miss  E)  

.040 

325 

14.50 

o 

.080 

5  724 

3400 

.300 

040 

130  00 

.368 

0 

2  043 

1170  0 

.001 

.085 

13.50 

0 

16.000 

64.0 

Cincinnati  Ohio  (Ohio  E  )  

.003 

.108 

14.00 

.260 

140.0 

Philadelphia  (Schuylkill  E.,  average  of  22) 

.010 

.100 

0 

.460 



133.4 

New  York,  weekly  average  for  1894  

.012 

.082 

2.47 

0 

.258 



81.6 

Water  Supplies,"  Mason,  p.  465. 


74  SANITARY   AND   APPLIED   CHEMISTRY 


DRINKING   WATER   AND   DISEASE 

It  should  be  noticed  in  the  first  place  that  while 
peaty  waters  contain  quite  large  quantities  of  organic 
matter,  this  is  not  considered  as  injurious  as  other  kinds 
of  organic  material.  The  best  authorities  seem  to  agree, 
however,  that  its  presence  does  tend  to  induce  diarrhoea 
and  malaria.  According  to  recent  investigations  the  preva- 
lence of  malaria  in  certain  localities  is  due  largely  to  the 
low  land  and  numerous  puddles  where  the  mosquitoes  that 
transmit  the  infection  have  a  chance  to  breed.1  It  should 
also  be  said  that  though  a  water  of  this  class  may  be  harm- 
less at  some  stages  of  its  history,  at  other  stages  it  may  be 
injurious  on  account  of  the  decomposition  that  has  taken 
place.  Another  water  containing  a  large  quantity  of  organic 
matter  is  the  so-called  sawdust  water,  which  is  obtained 
from  wells  sunk  in  "  made  "  land  in  the  vicinity  of  streams 
where  sawmills  have  been  located.  This  is,  without  doubt, 
injurious. 

In  regard  to  hard  waters,  the  opinion  seems  to  be  pre- 
dominant that  the  mortality  is  practically  uninfluenced  by 
hard  or  soft  water. 

In  many  localities,  waters  that  are  extremely  turbid  are 
used  for  domestic  purposes,  and  it  is  evident  that  they  are 
used  without  serious  injury,  when  we  consider  the  popula- 
tion and  the  death  rate  in  such  cities  as  Cincinnati,  Louis- 
ville, and  St.  Louis.  This  should  be  said,  however,  that 
while  these  waters  are  used  with  impunity  by  those  who  are 
accustomed  to  their  use,  strangers  are  frequently  affected 
seriously  for  a  time  by  the  use  of  such  waters. 

A  much  more  serious  class  of  impurities  is  those  which 
come  from  the  introduction  of  sewage  into  the  waters,  and 

1  "  Practical  Hygiene,"  Harrington,  p.  649. 


WATER  75 

although  they  may  be  perfectly  clear,  transparent,  and  of 
good  taste,  such  waters  are  often  extremely  dangerous.  The 
question  arises,  Shall  the  water  once  polluted  by  sewage  be 
again  used  for  human  consumption  ?  And  if  there  is  danger 
in  such  use,  What  is  its  extent,  and  can  such  danger  be 
avoided  ?  A  few  examples  of  pollution  of  water  by  sewage 
will  be  of  interest. 

In  1887 l  the  city  of  Messina,  Sicily,  was  visited  by  an 
epidemic  of  cholera.  Prom  September  10  to  October  25 
there  were  5000  cases  and  2200  deaths.  The  government 
investigated  this  epidemic,  and  it  was  found  that  though 
the  water  which  was  supplied  to  the  city  left  the  gathering 
grounds  in  the  mountain  of  good  quality,  part  of  it  was 
diverted  on  its  way  to  the  city,  and  used  by  the  washer- 
women of  the  vicinity  for  washing  clothes,  and  was  after- 
ward conducted  back  into  the  open  canal  which  supplied 
the  city.  As  soon  as  the  authorities  sent  tank  ships  to  the 
mainland  and  obtained  pure  water  for  use  in  the  city,  the 
plague  ceased  as  if  by  magic. 

In  1890  there  were  two  violent  epidemics  of  typhoid  fever 
in  the  valley  of  the  Tees  in  England.  The  country  which 
supplied  the  water  was  not  thickly  populated,  and  the  water 
was  apparently  good.  It  was  found,  however,  that  many 
of  the  towns  discharged  their  sewage  into  the  stream,  and 
in  dry  weather  the  stream  receded,  leaving  its  banks  dry 
and  exposed.  Here  the  filth  accumulated,  and  in  times  of 
high  water  this  was  swept  into  the  stream,  and  was  after- 
ward pumped  into  the  reservoirs  and  used  as  the  source  of 
water  supply.  It  was  noticed  that  an  "  increase  of  rainfall 
was  followed  by  an  increase  in  the  number  of  cases  of 
typhoid  fever  among  those  persons  using  the  Tees  water, 
after  an  interval  corresponding  to  the  incubation  period 
of  the  disease,  while  no  appreciable  result  was  noticed 

1  Mason  on  "Water  Supply,"  p.  24. 


76  SANITARY   AND   APPLIED   CHEMISTRY 

among  those  people  of  the  district  using  other  sources  of 
supply."  1 

One  of  the  most  interesting  cases  is  that  of  the  city  of 
Plymouth,  Pennsylvania,  containing  8000  population.  In 
a  few  weeks  there  were  more  than  1000  cases  of  typhoid 
fever  and  100  deaths.  The  water  supply  was  obtained 
from  a  mountain  brook.  There  were  but  few  houses  on  the 
banks  of  this  brook,  and  it  would  seem  that  the  water  was 
well  protected  from  sources  of  contamination.  On  investi- 
gation, it  was  learned  that  while  the  stream  was  frozen  a 
man  had  been  sick  with  typhoid  fever,  and  had  been  cared 
for  in  a  house  near  the  source  of  this  mountain  brook.  The 
discharges  were  thrown  upon  the  snow,  and  when  this 
melted  in  the  spring  the  filth  was  swept  into  the  stream. 
The  inhabitants  of  the  village  of  Plymouth  were  obliged  to 
use  this  water  for  a  time  as  their  source  of  supply,  instead 
of  the  Susquehanna  River,  so  the  typhoid  poison  was 
pumped  to  all  parts  of  the  city.  It  was  noticed  that  whole 
groups  of  families  using  well  water  escaped  entirely,  while 
those  using  the  city  water  were  afflicted  with  typhoid  fever. 
It  was  estimated  that  aside  from  the  deaths  that  occurred, 
the  money  losses  to  this  community  in  wages  and  care  of  the 
sick  was  over  $100,000. 

All  are  more  or  less  familiar  with  the  conditions  at  the 
time  of  the  terrible  outbreak  of  cholera  in  Hamburg,  Ger- 
many, in  1892.  The  city  had  a  population  of  640,000.  The 
epidemic  lasted  for  about  three  months,  and  the  total  num- 
ber of  cholera  cases  was  17,000,  with  50%  mortality.  Ham- 
burg is  close  to  the  city  of  Altona ;  in  fact,  these  two  together 
with  Wandsbeck  are  practically  one  city,  but  they  obtain 
their  water  from  different  sources.  Hamburg  pumps  water 
from  the  Elbe  River,  the  intake  being  just  south  of  the  city. 
Altona  pumps  its  water  from  the  Elbe  at  a  point  about  8 

1  Mason  on  "  Water  Supply,"  p.  27. 


WATER  77 

miles  below  that  at  which  the  river  receives  the  sewage  of 
the  three  cities ;  but  in  the  case  of  Altona  the  water  which 
has  received  the  sewage  from  a  population  of  800,000  people 
was  filtered  with  exceeding  care  before  being  delivered  to 
the  people.  It  was  interesting  to  notice  in  this  case  that  in 
some  sections  of  the  city,  people  supplied  with  the  Hamburg 
water  were  afflicted  with  cholera,  while  those  on  the  other 
side  of  the  same  street  using  the  Altona  water  were  not 
afflicted,  and  this  immunity  from  cholera  of  those  using  the 
Altona  water  was  noticeable  all  over  the  city. 

The  analysis  of  the  Hamburg  supply  showed  in  parts  per 
million :  — 

Free  ammonia 1.065 

Albuminoid  ammonia .293 

Nitrates     .                 26.430 

Chlorin 472.000 

The  case  of  the  outbreak  of  typhoid  fever  at  Lausen, 
Switzerland,  is  also  very  instructive.  The  source  of  the 
epidemic  was  traced  to  an  isolated  farmhouse  on  the  oppo- 
site side  of  the  mountain,  where  three  cases  of  the  fever 
occurred.  The  brook  which  ran  past  the  house  was  after- 
wards used  for  irrigating  some  meadows,  and  then  filtered 
through  the  intervening  mountain  to  a  spring  in  Lausen, 
from  which  all  the  people,  except  those  in  six  houses,  ob- 
tained their  water  supply.  In  the  six  houses  no  cases  of 
fever  occurred,  but  scarcely  one  of  the  other  houses  escaped. 
By  dissolving  a  large  amount  of  salt  in  the  water  on  the 
other  side  of  the  mountain,  and  observing  the  great  in- 
crease of  chlorin  in  the  spring  water,  the  source  of  the  in- 
fection was  traced,  and  to  show  how  thoroughly  the  water 
was  filtered,  a  quantity  of  flour  was  mixed  with  the  brook 
water,  and  not  a  trace  was  found  in  the  spring  water  at  the 
village.  This  showed  that  filtration  through  the  rocks  and 
soil  of  the  mountain  did  not  remove  the  dangerous  infection. 


78  SANITARY   AND   APPLIED  CHEMISTRY 

The  water  of  our  ordinary  domestic  wells  is  also  liable  to 
be  impure,  especially  in  a  thickly  populated  district.  Ma- 
terial from  cesspools  or  vaults  or  sewers  or  even  from  the 
surface  may  get  in  and  contaminate  the  water.  The  chief 
trouble  is  that  we  cannot  be  sure  of  the  water,  for  as  a  dis- 
trict becomes  more  thickly  populated  there  may  come  a 
time  when  the  soil  is  saturated  with  filth,  and  then  every 
rain  will  cause  some  of  this  to  flow  into  the  well. 

In  conclusion,  then,  any  source  of  supply  may  be  contami- 
nated, and  there  is  danger  in  the  use  of  well  waters  especially 
in  crowded  districts.  Numerous  diseases  are  distributed  by 
impure  waters,  and  in  any  case  of  an  epidemic  of  these  dis- 
eases that  are  propagated  by  germs,  the  water  supply  should 
be  very  carefully  examined,  and  it  is  always  advisable  at 
such  times  to  boil  the  water  before  using. 


CHAPTER  VI 
PURIFICATION  OF  WATER  SUPPLIES 

WATER  is  naturally  purified  by  sedimentation,  dilution, 
oxidation,  filtration,  vegetable  growth,  and  bacterial  action. 
The  extent  to  which  each  of  these  agencies  improves  the 
water  depends  on  a  variety  of  circumstances.  With  the 
deposit  of  mud  and  silt  there  is  often  carried  down  a  large 
amount  of  organic  matter ;  indeed,  the  presence  of  a  certain 
amount  of  suspended  matter  in  some  of  the  Western  rivers 
seems  to  assist  in  the  removal  of  organic  impurities.  Sedi- 
mentation alone,  however,  will  not  purify  an  unsafe  water. 

Dilution  of  a  small  stream  carrying  sewage  by  a  large 
stream  of  purer  water  seems  to  make  it  of  better  quality, 
but  really  the  organic  matter  is  simply  distributed  through 
a  larger  volume  of  water,  and  not  necessarily  destroyed. 

Oxidation,  by  a  rapid  fall,  or  by  exposure  to  the  air  in 
running  over  riffles,  as  in  a  shallow  stream,  has  been 
depended  upon  formerly  for  a  large  amount  of  purification. 
There  is  a  difference  of  opinion,  however,  as  to  the  extent 
to  which  oxidation  will  destroy  pathogenic  germs,  but  it 
usually  happens  that  these  conditions  are  very  favorable  to 
purification.  W.  C.  Young1  states,  as  the  result  of  his 
experiments,  that  the  removal  of  dissolved  organic  matter 
from  river  water  by  natural  means  is  extremely  slow.  The 
principal  agent  in  this  purification  is  the  growth  of  vegeta- 
ble organisms,  and  atmospheric  oxidation  has  little  effect. 

1  Jour.  Soc.  Chem.  2nd.,  Vol.  13,  p.  318. 
79 


80  SANITARY   AND   APPLIED   CHEMISTRY 

FILTRATION  AND   SOFTENING 

Water  may  be  further  purified  by  some  artificial  method 
of  filtration,  and  this  may  be  done  on  a  large  scale  by  a 
public  water  supply  company  in  a  much  more  economical 
and  efficient  manner  than  by  household  filtration. 

For  the  filtration  of  public  water  supplies,  some  of  the 
most  efficient  means  have  been  found  to  be,  — 

1.  Slow  sand  filtration. 

2.  Mechanical  filtration. 

3.  The  iron  process. 

4.  Clark's  process. 

In  the  slow  sand  filtration  system,  the  water  is  run  con- 
tinuously on  to  a  filter  made  of  coarse  gravel,  fine  gravel, 
and  sand,  suitably  underdrained.  When  a  filter  begins  to 
clog,  its  surface  is  cleaned  by  paring  off  a  fraction  of  an  inch 
of  sand.  In  the  use  of  the  filter  it  has  been  found  that  its 
efficiency  increases  for  some  time  after  it  is  first  installed, 
as  the  mat  or  slime  of  bacteria  and  organic  matter  increases. 
The  top  layer,  however,  does  not  do  all  the  work  of  filtra- 
tion, as  was  shown  by  Eiensch  in  the  case  of  the  Altona 
filters.  He  found  that  the  unfiltered  water  contained  36,320 
microbes  per  cubic  centimeter,  and  after  passing  through 
the  upper  or  slime  layer  of  the  filter  it  contained  1876  mi- 
crobes, and  finally  the  effluent  contained  only  44  microbes 
per  cubic  centimeter. 

For  the  proper  working  of  this  system  quite  a  large  area 
of  filter  beds  is  required,  as  it  must  be  so  arranged  that 
some  beds  can  be  cleaned  while  others  are  in  use.  The  area 
of  the  beds  in  Hudson,  New  York,  for  instance,  is  30,000  sq. 
ft.  An  average  rate  of  filtration  of  about  three  million  gal- 
lons per  acre  per  24  hours  is  usually  attained. 

As  to  the  efficiency  of  this  system  of  filtration,  attention 
may  be  called  again  to  the  Altona  case,  where  ten  of  these 


PURIFICATION   OF   WATER  SUPPLIES  81 

filters  are  used.  The  average  number  of  germs  in  the  unfil- 
tered  water  was  28,667  and  in  the  filtered  water  only  90; 
so  99.69%  of  the  germs  were  removed.  The  removal  of  the 
bacteria  is  not  due  simply  to  straining,  but  the  conditions 
within  the  filter  are  unfavorable  to  the  life  of  the  bacteria. 
The  food  material  for  bacterial  growth  is  gradually  taken 
away,  and  the  water  actually  improves  in  quality  as  it  flows 
through  the  pipes  to  the  consumer.  In  Lawrence,  Massa- 
chusetts, it  is  stated  that  the  mortality  from  typhoid  fever 
has  been  reduced  40%  since  this  system  of  filtration  was 
introduced. 

In  order  to  avoid  the  great  expense  of  erecting  filtering 
basins,  filtration  galleries  are  sometimes  built  beneath  the 
surface  along  the  banks  of  a  stream,  and  so  arranged  that  the 
water  that  percolates  through  the  sand  into  the  gallery  can 
be  pumped  into  the  service  pipes.  These  galleries,  however, 
are  not  easily  inspected  and  are  liable  to  get  out  of  repair  or 
become  clogged. 

Mechanical  filtration  may  be  performed  either  with  or 
without  the  use  of  alum  or  some  other  coagulant.  Here 
the  water  is  forced  through  a  bed  of  sand  contained  in  a 
tank,  and  after  the  filter  becomes  clogged  it  can  be  cleaned 
in  about  fifteen  minutes  by  reversing  the  current  of  water. 
It  is  interesting  to  notice  that  in  this  process  the  "  bacterial 
jelly"  on  the  top  of  the  filter  beds  is  replaced  by  an  artificial 
inorganic  jelly  of  aluminum  hydroxid,  which  entangles  the 
bacteria  and  at  the  same  time  reduces  the  amount  of  organic 
matter  in  the  water.  The  use  of  alum  is  applicable  only  to 
those  waters  possessing  temporary  hardness.  In  that  case 
the  calcium  bicarbonate  will  cause  the  precipitation  of  the 
aluminum  hydroxid. 

Experiment  53.  The  action  of  a  coagulant  may  be 
illustrated  by  putting  a  few  grams  of  alum  into  a  sample  of 


82  SANITARY   AND   APPLIED   CHEMISTRY 

water,  and  adding  to  it  enough  of  a  tincture  of  cochineal 
to  give  it  a  strong  red  color.  Add  to  this  ammonium 
hydroxid  in  excess,  and  allow  to  stand  for  some  time, 
when  the  coloring  matter  will  be  precipitated  with  the 
aluminum  hydroxid,  A1(OH)3,  leaving  the  solution  colorless. 

In  the  iron  process  the  water  is  brought  in  contact  with 
spongy  iron,  and  the  result  is  the  precipitation  of  ferric 
hydroxid,  which  carries  down  with  it  most  of  the  organic 
matter.  The  precipitate  may  be  removed  either  by  sedi- 
mentation or  by  filtration  through  sand. 

In  the  Anderson  process  ferric  hydrate  is  formed  in  the 
water  by  the  combined  action  of  iron  scraps  and  air,  and 
the  precipitate  is  filtered  out. 

Experiment  54.  To  a  dilute  solution  of  ferric  chlorid, 
add  an  excess  of  ammonium  hydroxid.  The  reddish  brown 
precipitate  of  ferric  hydroxid  produced  is  similar  to  that  in 
the  iron  process. 

Clark's  process  for  softening  water  depends  on  the  pre- 
cipitation of  a  large  part  of  the  carbonates  by  the  addition 
of  calcium  hydroxid  (limewater)  in  accordance  with  the 
reaction  CaH2(C03)2  +  Ca  (OH)2  =  2  CaCOs  +  2  H20.  The 
precipitate  of  calcium  carbonate  is  then  allowed  to  settle,  or 
is  filtered  off.  (See  p.  67,  also  Soap.)  A  large  proportion 
of  the  organic  matter  is  carried  down  with  this  precipitate. 

Experiment  54  a.  Pass  a  current  of  carbon  dioxid  through 
a  dilute  solution  of  calcium  chlorid  till  the  precipitate  at 
first  formed  is  dissolved.  Add  to  this  solution  an  excess  of 
limewater  and  notice  the  formation  of  the  precipitate. 

Where  household  filtration  is  a  necessity,  some  device  of 
porous  stone  or  tile,  sand  or  animal  charcoal,  may  be  used. 
The  filter  should  be  of  such  construction  that  if  of  stone 
it  can  be  readily  cleaned  with  hot  water  and  a  stiff  brush, 
or  by  thoroughly  washing  if  of  sand  or  similar  material. 


PURIFICATION   OF   WATER   SUPPLIES  83 

The  Pasteur-Chamberland  filter,  which  is  made  of  unglazed 
porcelain,  is  one  of  the  most  efficient  filters,  as  bacteria  are 
practically  removed  from  the  water  by  its  use.  The  Worms, 
or  Fisher,  filter,  made  by  the  use  of  plates  of  artificial  stone, 
has  also  proved  efficient.  It  is  of  importance  to  remember 
that  waters  that  are  bad  from  the  presence  of  organic  matter 
may  be  made  safe  by  thoroughly  boiling,  and  also  by  distil- 
lation, and  condensation  of  the  steam. 

Ground  water  should  be  stored  in  dark  reservoirs,  as 
under  these  conditions  the  algae  and  other  troublesome  or- 
ganisms, which  injure  the  water,  do  not  develop  as  rapidly. 
Surface  water  often  improves  in  quality  when  stored  in 
clean  open  reservoirs  where  the  sides  have  been  thoroughly 
cleared  of  vegetation.  The  effect  of  mud  deposits  in  storage 
reservoirs  is  not  necessarily  harmful.  If,  however,  these 
deposits  furnish  food  for  and  encourage  the  growth  of  organ- 
isms that  by  their  development  impart  a  disagreeable  taste 
and  odor  to  the  water,  they  should  be  removed. 

The  good  effect  of  freezing  has  been  very  much  over- 
estimated, according  to  Prudden.1  Clear,  transparent  ice, 
from  the  surface  of  an  open  body  of  water,  when  melted, 
yields  about  10%  as  many  bacteria  as  were  present  in  the 
original  water.  If  a  pond  freezes  solid  to  the  bottom,  all 
the  impurities  that  were  in  the  water  will  be  in  the  ice. 

1  Medical  Secord,  March  26,  1887. 


CHAPTER  VII 


THE  only  practical  methods  that  have  been  proposed  for 
the  disposal  of  the  "  wastes  of  animal  life "  are  the  "  dry 
earth"  system  and  the  "water  carriage"  system.  The 
former  may  be  utilized  in  detached  houses  where  no  better 
method  is  available.  The  water  carriage  system  is  prefer- 
able, both  from  the  standpoint  of  economy  and  that  of 
sanitary  efficiency. 

The  organic  material  that  accumulates  in  the  waste  of 
modern  dwellings  is  of  such  a  character  that  it  must  be  very 
quickly  removed  or  it  will  prove  a  menace  to  health. 
Sewage  may  be  defined  as  "  a  complex  mixture,  with  water, 
of  the  waste  products  of  life  and  industry  from  densely 
settled  communities."  The  only  solids  of  importance  which 
this  sewage  carries  are  those  which  are  susceptible  of  solu- 
tion in  water,  or  which  become  disintegrated  in  transit. 
Sewage  consists  very  largely  of  water  which  acts  as  a 
vehicle  to  carry  away  a  small  quantity  of  other  substances. 
In  1000  parts  of  sewage  it  is  estimated  that  there  is  1  part 
of  mineral  matter  and  1  part  of  organic  matter,  leaving 
998  parts  of  pure  water.  Now,  the  mineral  matter  con- 
tained in  sewage  is  practically  of  no  importance,  so  that  all 
our  efforts  are  directed  toward  the  removal  of  the  1  part  of 
organic  matter  in  1000  parts  of  water.  The  only  really 
dangerous  substances  in  sewage  are  the  disease-producing 
organisms,  but  the  gases  given  off  as  the  result  of  decompo- 
sition are  extremely  disagreeable.  Sewer  gas  is  not  as  liable 

84 


SEWAGE  DISPOSAL  85 

to  contain  microorganisms,  which  will  be  injurious  to  the 
health,  as  was  formerly  supposed. 

The  material  which  issues  from  the  sewers  of  large  cities 
contains  no  dissolved  oxygen  and  no  oxidized  nitrogen. 
The  reason  for  this  is  that  the  available  oxygen  of  the  water 
has  been  removed  in  oxidizing  a  portion  of  the  carbon  of 
the  organic  matter,  but  it  has  not  sufficed,  also,  for  the 
oxidation  of  the  nitrogen,  and  further  oxidation  can  go  on 
only  by  the  addition  of  more  oxygen  to  the  water.  If  the 
nitrogenous  material  in  the  sewers  is  represented  by  ammo- 
nia, then  the  following  equation  may  be  written :  — 

2  NH3  +  4  02  =  2  HN03  +  2  H20. 

Now  this  nitric  acid,  coming  in  contact  with  the  calcium 
carbonate   of  the  soil  and  of    the  water  is   decomposed 

thus :  — 

CaC03  +  2  HN03  =  Ca(N03)2  +  H20  +  C02. 

The  most  modern  theory  for  the  purification  of  sewage  is 
that  it  is  carried  on  very  largely  by  bacteria,  and  even  this 
process  of  nitrification,  as  it  is  called,  which  the  above  equa- 
tion represents,  cannot  go  on  without  the  intervention  of 
nitrifying  bacteria,  and  this  class  of  organisms  must  work 
in  a  medium  containing  a  sufficient  quantity  of  free  oxygen. 
This  purification  may  take  place  in  water,  when  there  is  a 
sufficient  quantity  of  the  free  oxygen  in  proportion  to  the 
filth  handled.  In  soil  this  nitrification  is  of  the  utmost  im- 
portance in  the  process  of  preparing  it  for  the  growth  of 
plants,  and  in  keeping  up  its  fertility. 

DISPOSAL   OF   SEWAGE  BY  DILUTION 

If  the  stream  into  which  the  sewage  is  poured  is  small, 
and  the  current  of  low  velocity,  the  result  will  be  the  pro- 
duction of  a  very  disagreeable  odor  from  the  decomposition 


86  SANITARY   AND   APPLIED   CHEMISTRY 

of  the  sewage,  but,  if,  on  the  other  hand,  the  flow  of  the 
stream  is  large,  this  sewage  will  be  distributed  through  so 
much  water  that  we  shall  not  find  any  offensive  odor  arising 
from  it.  It  has  been  estimated  that  a  stream  which  carries 
off  sewage  should  have  a  volume  of  from  twenty-five  to 
thirty-five  times  that  of  the  sewage ;  the  proportion,  how- 
ever, depends  on  the  amount  of  free  oxygen  that  is  carried 
by  the  stream  and  several  other  factors.  The  amount  of 
water  needed  to  carry  off  the  sewage  can  be  calculated 
readily,  by  knowing  the  amount  of  water  supplied  to  the 
town,  as  it  has  been  found  under  normal  conditions,  that 
the  volume  of  sewage  is  practically  the  same  as  the  amount 
of  water  supplied. 

In  the  case  of  the  city  of  Milwaukee,  as  an  illustration, 
for  many  years  the  sewage  was  turned  into  the  Milwaukee 
River,  a  small  stream,  which  became  extremely  foul,  but 
arrangements  were  made  to  pump  a  large  amount  of  water 
from  the  lake  into  the  river  3^  miles  inland,  thus  supplying 
26  times  as  much  water  as  the  volume  of  the  sewage,  and 
by  so  doing  the  sewage  was  flushed  out  with  the  water, 
and  the  odor  disappeared.  To  handle  the  sewage  of  Chicago 
it  would  be  necessary  to  follow  the  same  plan,  and  have  25 
times  as  much  water  in  the  drainage  canal  as  the  sewage 
of  the  city. 

The  objection  to  the  disposal  of  sewage  in  this  way 
is,  of  course,  the  rendering  of  a  river  water  so  impure. 
Although  some  experimenters  have  shown  that  water  after 
running  20  miles  is  quite  completely  purified  by  the  process 
of  oxidation  and  nitrification,  others  claim  that  even  by  run- 
ning ten  times  as  far,  the  pathogenic  germs  would  not  be  re- 
moved, and  there  is  a  natural  repugnance  against  using,  for 
drinking  purposes,  water  that  has  been  at  any  time  contami- 
nated by  sewage. 


SEWAGE  DISPOSAL  87 

DISPOSAL   OF    SEWAGE   BY   IRRIGATION 

Another  method  for  disposal  of  sewage  is  by  irrigation. 
It  is  well  known  that  there  is  a  large  amount  of  available 
fertilizing  material  in  the  sewage  of  the  modern  city ;  for 
instance,  the  sewage  of  London  is  said  to  be  worth  annually 
$14,000,000  for  fertilizing  purposes.  Some  hold  that  sewage 
is  not  of  such  great  intrinsic  value  after  all,  for  it  has  been 
practically  found  that  it  is  not  possible  to  handle  very  large 
quantities  of  sewage  upon  a  farm,  and  that  the  process 
cannot  be  applied  upon  a  very  large  scale.  Another  disad- 
vantage is  that  when  there  is  a  large  amount  of  rain,  or 
when  the  water  freezes,  the  process  is  very  much  interfered 
with,  and  the  system  to  be.  satisfactory  must  be  carried  on 
without  any  interruption  day  after  day,  so  as  not  to  allow 
any  offensive  matter  to  collect.  The  late  Colonel  Waring  1 
states  that  an  acre  of  land  will  be  required  to  care  for  the 
sewage  of  from  250  to  500  persons,  and  when  the  question  of 
growing  crops  is  of  secondary  importance,  and  the  soil  is 
porous  and  sandy,  the  sewage  of  1000  to  1500  can  be  purified 
on  an  acre  of  ground.  The  city  of  Berlin  has  set  aside 
20,000  acres  for  a  sewage  farm,  and  it  is  said  that  it  actually 
receives  a  yearly  profit  of  $60,000  from  the  operation. 

INTERMITTENT   FILTRATION 

The  next  method  for  disposal  of  sewage  is  by  intermittent 
filtration.  This  process  is  a  natural  one,  because  it  depends 
for  its  success  upon  the  prevalence  of  certain  natural  con- 
ditions; that  is,  the  presence  of  oxygen  and  living  micro- 
organisms. If  we  allow  sewage  to  run,  for  some  time,  upon 
a  filter  bed  composed  of  sand  and  gravel  and  then  turn  this 
sewage  on  to  another  filter  bed  and  allow  the  water  to  run 
out  of  the  first  bed  and  the  air  to  enter  the  spaces  between  the 

1  Harrington,  "Practical  Hygiene,"  p.  496. 


88  SANITAEY  AND   APPLIED  CHEMISTRY 

grains  of  sand,  we  furnish  the  means  for  the  growth  of  the 
microorganisms.  This  is  much  more  satisfactory  than  at- 
tempting to  filter  continuously  through  the  same  filter  bed. 
As  an  illustration  it  was  shown  in  one  case  that  by  the  use 
of  this  process  where  31,400  gal.  of  sewage  per  acre  was  fil- 
tered, 98.6%  of  the  organic  impurity  was  removed,  and  99% 
of  the  bacteria. 

THE  SEPTIC   TANK 

There  is  a  modification  of  the  above  method  which  is 
known  as  the  use  of  the  septic  tank,  in  which  the  sewage  is 
liquefied  by  being  stored  first  in  the  sunshine  or  in  the  air, 
allowing  the  aerobic  bacteria  to  work,  and  afterward  in  a 
closed  tank  where  another  class  of  bacteria  (the  anaerobic) 
carry  on  their  purifying  process.  This  material  is  then  run 
upon  filter  beds,  and  a  very  pure  effluent  is  the  result.  Some 
engineers  prefer  to  run  the  sewage  first  into  a  closed  tank, 
through  which  it  requires  from  12  to  24  hours  to  pass,  and 
where  a  thick  scum  covers  the  surface,  gases  are  given  off, 
and  very  complete  decomposition  takes  place.  The  effluent 
from  this  tank  is  then  run  on  to  filter  beds.  It  is  to  be  noted 
that  both  aerobic  bacteria,  or  those  which  work  in  light  and 
air,  and  anaerobic  bacteria  assist  in  the  purification  of  sewage. 

PRECIPITATION   OF   SEWAGE 

Another  method  for  sewage  disposal  is  by  chemical  pre- 
cipitation. For  this  purpose  such  substances  as  ferrous 
sulfate,  ferric  sulfate,  lime,  or  alum  are  used.  It  was 
at  first  proposed  to  utilize  the  precipitated  material  as  a 
fertilizer,  and  considerable  money  has  been  spent  in  pre- 
paring this  material  and  extracting  the  water  from  it  by 
pressure.  This  process,  however,  has  not  been  found  to  be 
very  satisfactory,  and  improvements  must  be  carried  still 
farther  before  this  method  for  disposal  of  sewage  will  be 
extensively  adopted. 


SEWAGE   DISPOSAL  89 

To  recapitulate,  for  the  purification  of  sewage,  we  must 
depend  largely  upon  the  work  of  bacteria  often  in  the  pres- 
ence of  oxygen,  and  any  plan  which  utilizes  the  work  of 
these  organisms  to  the  greatest  extent,  and  furnishes  the 
most  complete  conditions,  for  work  in  this  way,  will  be 
successful. 

DISPOSAL  OF  HOUSEHOLD  -WASTE 

A  method  for  disposing  of  garbage  or  household  waste 
economically  has  long  perplexed  the  health  authorities. 
Two  conditions  may  be  considered  :  that  of  disposing  of  it 
on  the  premises  where  it  is  produced,  and  that  by  the  city 
authorities. 

Several  methods  have  been  used  for  disposal  of  refuse 
without  removal  from  the  premises.  Among  these  the  pro- 
cess of  burning  in  the  stove,  range,  or  furnace,  either  with 
or  without  previous  drying  is  suggested.  This  is  efficient 
and  practical  if  the  amount  of  such  waste  material  is  not 
too  large,  and  if  a  good  fire  is  maintained.  In  summer, 
when  there  is  naturally  a  larger  amount  of  refuse,  and  the 
fires  are  not  kept  burning  so  continuously,  it  is  often 
difficult  to  handle  garbage  in  this  way. 

A  modification  of  the  above  method  consists  in  having  an 
enlargement  of  the  smoke  pipe  of  the  stove  at  the  elbow, 
and  to  introduce  into  this,  through  an  opening  in  the  side,  a 
perforated  basket  containing  the  garbage.  The  material 
soon  becomes  dry  and  is  partially  charred,  and  then  may 
be  taken  out  and  put  into  the  stove,  where  it  is  useful 
as  fuel. 

In  some  cities  the  plan  of  building  brick  or  stone  furnaces 
in  the  yard,  for  the  sole  purpose  of  burning  rubbish,  has 
been  adopted  with  great  success. 

Another  method  of  disposal  is  by  burying  in  the  soil,  and 
as  the  decomposition  takes  place  rapidly,  if  only  a  few 


90  SANITARY   AND   APPLIED   CHEMISTRY 

inches  of  soil  is  placed  over  the  material,  no  obnoxious  odor 
arises  to  contaminate  the  air.  When  one  hole  is  filled,  it  is 
covered  and  another  is  dug  beside  it ;  but  these  holes  must 
not  be  too  deep  or  too  large. 

If  the  city  or  village  undertakes  to  dispose  of  the  gar- 
bage, usually  great  expense  is  incurred,  as  the  quantity  is 
very  large.  For  instance,  in  Manhattan  alone  the  dry  refuse 
amounts  to  1,000,000  tons  in  a  year,  and  the  garbage  is 
175,000  tons  per  year.1 

Disposing  of  garbage  to  farmers  for  feeding  of  stock  or 
swine  is  also  practical.  This  involves  a  long  haul  of  ill- 
smelling  material  through  the  streets,  and  is  particularly 
objectionable  if  the  material  is  not  collected  every  day. 

In  some  localities  garbage  is  loaded  on  to  scows,  towed 
out  to  sea  and  dumped,  but  here  the  incoming  tide  may 
throw  the  decomposing  material  back  on  the  shore. 

There  is  a  very  valid  objection  to  using  such  refuse, 
even  if  the  more  perishable  material  is  excluded,  for  filling 
in  the  so-called  "  made  land,"  as  decomposition  will  continue 
for  years  in  this  soil,  and  the  air  of  dwellings  built  upon 
it  will  be  contaminated. 

Cremation  has  been  adopted  in  many  cities  with  good  suc- 
cess. In  1899,  81  communities  in  Great  Britain  were  em- 
ploying incineration  as  the  chief  means  for  disposal  of 
refuse,  and  76  of  them  turned  the  developed  heat  from  the 
combustion  of  this  refuse  to  some  useful  purpose,  such  as 
making  steam  to  run  electric  lighting  plants,  for  sewage 
pumping  works,  for  grinding  road  material,  and  for  use  in 
the  process  of  disinfection  of  clothing.2 

Another  plan  is  by  "  reduction,"  in  which  method  the  gar- 
bage is  dried  in  steam-jacketed  cylinders,  the  dried  residue 
then  extracted  with  naphtha,  and  the  grease  thus  removed  is 

1  Price,  "  Handbook  on  Sanitation,"  p.  49. 

2  Harrington,  "Practical  Hygiene,"  p.  609. 


SEWAGE  DISPOSAL  91 

saved  as  a  valuable  product.  The  residue  is  again  dried  and 
worked  up  into  a  fertilizer.  It  is  well  to  remember  that 
such  quickly  decomposing  material  as  garbage  should  be 
immediately  removed  under  sanitary  inspection,  whether 
any  financial  profit  comes  to  the  city  from  its  treatment 
or  otherwise. 


CHAPTER  VIII 
CLEANING:    SOAP,    BLUING 

WITH  our  modern  knowledge  of  the  means  of  transmitting 
disease,  filth  is  something  to  be  avoided,  as  it  assists  in  the 
spread  of  infection  from  one  locality  to  another.  The  love 
of  cleanliness,  which  is  considered  a  sign  of  a  higher  civili- 
zation, is,  no  doubt,  the  outgrowth  of  years  of  experience 
with  the  dangers  of  dirt.  This  abhorrence  for  filth  is  a 
sanitary  safeguard:  it  protects  the  body,  the  air,  the  water 
supply,  and  the  food  supply.  As  man  has  advanced  he  has 
demanded  some  cleansing  agent  for  the  body,  the  utensils, 
and  the  clothing,  and  so  a  great  industry  has  developed  for 
the  preparation  of  these  agents. 

Substances  used  for  cleaning  act  either  mechanically  or 
chemically  to  remove  the  offensive  materials.  In  the  use  of 
soap  and  sand,  for  scouring,  there  is  a  combination  of  these 
methods ;  and,  in  fact,  when  the  chemical  loosens  up  the 
fibers  or  sets  free  the  dirt,  some  mechanical  process  is 
often  required  to  remove  it. 

Most  of  the  polishing  and  cleaning  powders  on  the  market 
depend,  for  their  efficiency,  upon  the  action  of  a  very  finely 
divided  substance  like  silica,  precipitated  chalk,  or  rouge. 
This  is  mixed  with  some  fat  or  oil;  thus,  some  "Putz  Pom- 
ades" contain  rouge,  some  finely  divided  silica,  and  a  per- 
fumed fat.  In  the  choice  of  a  polishing  material,  one  should 
be  selected  that  is  so  finely  divided  that  it  will  not  scratch 
the  metal.  Dry  sodium  bicarbonate  (baking  soda)  can  be 
safely  used  for  cleaning  and  polishing. 

92 


CLEANING:     SOAP,   BLUING  93 

Borax,  Na2B407,  added  to  water,  greatly  aids  in  the  removal 
of  dirt,  in  special  cases.  Ammonium  hydroxid  (aqua  am- 
monia) is  also  used  for  the  same  purpose,  and  as  it  forms  a 
soap  with  the  oily  matters  of  the  skin  or  of  the  fabrics 
washed,  it  is  a  convenient  cleaning  agent.  A  teaspoonful  of 
ammonia  to  a  quart  of  water  is  an  excellent  wash  for  wood 
work,  and  may  be  used  to  brighten  carpets  or  rugs.  Much 
of  the  "household  ammonia"  on  the  market  is  of  a  very  low 
grade,  and  so  it  is  always  advisable  to  purchase  ammonia 
from  a  druggist. 

A  cleaning  material  should  not  only  remove  the  grease  or 
dirt,  but  it  must  be  of  such  a  nature  that  it  will  not  injure 
the  article  cleaned.  From  the  recent  work  of  Mrs.  Rich- 
ards,1 many  of  the  following  suggestions  are  taken. 

In  some  cases,  as  with  wood,  leather,  metal,  etc.,  the 
dirt  does  not  penetrate  into  the  interior,  but  remains 
on  the  surface;  in  other  cases  the  whole  fabric  is  filled  with 
dust  and  grease.  All  polished  wood  surfaces,  except  those 
finished  with  wax,  may  be  cleaned  with  a  weak  solution  of 
ammonia,  or  soap,  but  they  should  never  be  treated  with 
a  strong  alkali. 

As  solvents  for  grease,  either  kerosene  or  turpentine  may 
be  used,  and  should  be  applied  with  a  soft  cloth.  Painted 
surfaces,  especially  if  white,  may  be  cleaned  with  a  little 
"  whiting,"  CaCOg,  which  can  be  applied  with  a  piece  of 
cheese  cloth.  The  wood  is  afterward  washed  with  water 
and  wiped  dry.  Painted  walls  if  painted  with  oil  paints 
can  be  cleaned  in  the  same  way,  but  "tinted"  walls,  since 
water  colors  are  used,  are  disfigured  by  this  treatment. 

Leather  may  be  kept  bright  and  clean  by  the  use  of 
kerosene,  or  occasionally  a  little  oil.  Marble  may  be 
scoured  with  sand  soap,  and  finally  polished  with  a  coarse 
flannel.  It  should  not  be  forgotten  that  marble  is  calcium 

1  Richards  and  Elliott,  "The  Chemistry  of  Cooking  and  Cleaning." 


94  SANITARY   AND   APPLIED   CHEMISTRY 

carbonate,  CaC03,  and  consequently  should  never  be  treated 
with  an  acid,  or  even  an  acid  fruit  juice.  Metals  can  usually 
be  cleaned  with  a  hot  alkaline  solution  or  a  little  kerosene. 
To  clean  glass,  .it  may  be  covered  with  a  paste  of  whiting, 
ammonia,  and  water,  and  after  it  is  dry  this  may  be  rubbed 
off  with  a  woolen  cloth  or  with  paper.  Kerosene  is  excellent 
for  this  purpose,  especially  in  the  winter  when  the  water 
would  freeze. 

Household  fabrics  are  often  washed  with  alkaline  solu- 
tions or  with  soap.  In  some  cases  naphtha  may  be  used 
for  washing  such  fabrics.  As  some  of  the  solvents,  such  as 
naphtha,  benzine,  turpentine,  and  gasoline  are  frequently 
used  for  cleaning,  and  removing  grease,  it  is  extremely 
important  to  remember  that  they  are  all  very  volatile,  and 
that  the  vapors  may  take  fire  from  a  lamp,  gas  jet  or 
stove,  even  if  at  some  distance.  On  this  account  work  of 
this  kind  should  be  done  by  daylight  and  out  of  doors,  if 
possible.  Many  serious  burns  occur  from  lack  of  these 
precautions. 

In  the  use  of  the  volatile  solvents  like  gasoline,  enough 
should  be  used  to  cover  a  large  portion  of  the  goods,  and 
if  possible  afterwards  wash  thoroughly  with  water. 

To  remove  stains,  spots,  and  tarnish,  a  little  knowledge  of 
chemistry  will  serve  an  excellent  purpose.  Since  grease  is 
readily  absorbed  by  blotting  paper,  spots  may  often  be  re- 
moved from  fabrics  by  placing  the  goods  between  two  pieces 
of  blotting  paper,  and  then  heating  with  a  warm  iron. 
French  chalk  will  sometimes  absorb  the  grease,  especially  if 
the  spots  are  fresh.  Grease  may  also  be  removed  by  the 
use  of  hot  water  and  soap,  ammonia,  or  even  borax.  If 
there  is  danger  that  these  solvents  will  injure  the  goods 
or  the  colors,  it  is  better  to  use  some  solvent  such  as 
chloroform,  ether,  alcohol,  turpentine,  benzine,  or  naphtha. 
Ether  and  chloroform  are  better  adapted  to  the  more  delicate 


CLEANING:     SOAP,   BLUING  95 

fabrics.  "  The  troublesome  '  dust  spot '  has  usually  a  neg- 
lected grease  spot  for  its  foundation.  After  the  grease  is 
dissolved  the  dust  must  be  cleaned  out  by  thorough  rinsing 
with  fresh  liquid  or  by  brushing  after  the  spot  is  dry."  1 

Since  paints  consist  of  oil  and  some  coloring  matter  and 
lead  or  zinc  oxides,  paint  spots  should  be  treated  with  a  sol- 
vent for  the  oil,  and  then  the  coloring  matter  can  be  brushed 
off.  Fresh  spots  may  be  treated  with  turpentine,  benzine, 
naphtha,  or  gasoline,  but  old  paint  spots  must  be  softened 
with  oil  or  grease,  and  may  then  be  removed  by  the  appro- 
priate solvent.  Pitch,  tar,  or  varnish  may  be  treated  with 
oil,  and  then  be  dissolved  out  with  turpentine. 

Sugar  deposits  are  soluble  in  warm  water.  If  acids  have 
destroyed  the  color  of  goods,  this  may  usually  be  restored 
by  ammonia,  and  dilute  alcohol  may  be  used  in  the  same 
way  for  the  stains  from  fruit. 

Ink  spots  would  not  be  so  difficult  to  remove  if  we  knew 
in  advance  the  composition  of  the  ink.  Fresh  ink  usually 
dissolves  in  cold  water,  though  sometimes  sour  milk  is  more 
efficient.  Ink  stains  may  also  be  removed  with  blotting  paper 
or  some  absorbent.  Ink  stains  on  marble  may  be  treated 
with  turpentine,  baking  soda,  or  strong  alkalies,  or  a  paste 
may  be  made  with  the  alkali  and  turpentine,  and  this  may 
be  left  for  some  time  in  contact  with  the  spot,  and  finally 
washed  off  with  water.  A  dilute  solution  of  oxalic  acid  may 
often  be  successfully  used  to  remove  either  ink  stains  or  iron- 
rust  spots. 

If  there  is  much  iron  in  the  water  supply,  this  may  be 
removed  from  bowls  or  other  porcelain  ware  by  the  use  of 
hydrochloric  acid,  then  rinse  with  water,  and  finally  with  a 
solution  of  soda. 

Silver  is  readily  tarnished  by  sulfur,  either  from  eggs, 
or  from  rubber  bands   or  elastic,  or  sometimes  from  the 

1  Richards  and  Elliott,  loc.  cit. 


96  SANITARY   AND   APPLIED   CHEMISTRY 

sulfur  compounds  in  the  illuminating  gas.  The  sulfid  of 
silver  thus  formed  is  grayish  to  black.  Silver  thus  tarnished 
should  be  rubbed  with  moist  common  salt  before  washing, 
thus  forming  a  silver  chlorid,  which  is  then  washed  in  am- 
monia, in  which  it  is  soluble. 

For  cleaning  and  polishing  brass  and  copper,  nothing  is 
better  than  oil  and  rotten-stone,  and  most  of  the  good  pol- 
ishes on  the  market  are  made  from  these  materials,  with  al- 
cohol, turpentine,  or  soap.  Kerosene  is  useful  in  keeping 
metals  bright,  as  well  as  glass  and  wood.  Aluminum 
may  be  cleaned  by  the  use  of  whiting  or  any  silver  polish, 
but  alkalies  should  not  be  used  upon  this  metal.  Aluminum 
does  not  readily  tarnish.  As  it  does  not  rust,  with  ordinary 
care  it  will,  in  a  kitchen  utensil,  last  for  many  years. 

Experiment  55.  To  remove  an  iron-rust  spot  from  a  piece 
of  goods,  stretch  the  cloth  over  a  dish  containing  hot  water, 
then  as  the  steam  arises  and  the  goods  become  moist,  drop 
a  little  muriatic  acid,  HC1,  upon  the  rust  spot  with  a  medi- 
cine dropper ;  after  a  moment  lower  it  into  the  water.  If 
the  spot  is  not  removed,  repeat  the  operation,  then  rinse  in 
clear  water,  and  finally  in  a  dilute  solution  of  ammonia  to 
neutralize  any  acid  that  might  remain  and  injure  the  goods.1 

Iron-rust  stains  may  often  be  completely  removed  from 
delicate  fabrics  by  the  use  of  lemon  juice  and  common 
salt. 

SOAP 

Water,  and  a  few  other  solvents,  are  used  to  remove  dirt, 
or,  as  it  is  sometimes  called,  "matter  out  of  place."  Some 
of  these  foreign  substances  readily  dissolve  in  the  water ; 
others,  like  the  fats,  will  dissolve  in  ether  or  gasoline;  and 
still  others,  as  the  resins,  will  dissolve  in  alcohol.  Some 
form  of  alkali,  such  as  wood  ashes,  was  formerly  used  with 

1  Richards  and  Elliott. 


CLEANING:  SOAP,  BLUING        97 

the  water,  to  assist  in  removing  the  dirt.  It  was  found, 
however,  that  this  had  a  very  destructive  action  on  the  goods, 
so  a  "  saponified  "  fat,  the  product  produced  by  the  action  of 
an  alkali  on  a  fat,  or  what  we  call  soap,  came  into  use. 
This,  when  well  made,  does  not  injure  the  goods.  Soap  was 
used  instead  of  the  lye  from  the  lixiviation  of  ashes,  long 
before  the  chemistry  of  the  process  became  known.  It  was 
not  till  1813  that  Chevreul  published  his  scientific  researches 
on  the  composition  of  fats  and  the  process  of  soap-making. 
The  raw  materials  used  in  soap  manufacture  are  an  alkali 
known  as  "  caustic  alkali,"  which  may  be  either  sodium  hy- 
droxid  (NaOH),  which  makes  a  hard  soap,  or  potassium 
hydroxid  (KOH),  which  makes  a  soft  soap.  These  are 
made  by  boiling  the  carbonate  with  slaked  lime,  in  accord- 
ance with  the  equation :  — 

Na2C03+Ca(OH)2=CaC03+2  NaOH. 

From  this  mixture  the  calcium  carbonate  settles  out,  and 
the  solution  of  the  caustic  alkali  is  boiled  down  to  a  solid, 
and  is  put  upon  the  market  under  the  name  of  "concentrated 
lye,"  or  the  concentrated  solution  is  used  directly  by  the 
soap  maker. 

More  recently  caustic  soda  has  been  made  directly  by  the 
electrolysis  of  sodium  chlorid,  NaCl.  The  sodium  deposited 
at  one  pole  is  dissolved  in  water,  and  the  chlorin  is  used  for 
making  bleaching  powder. 

The  second  ingredient  of  a  soap. is  either  a  vegetable  or 
animal  fat  or  oil  or  a  resin.  Such  oils  as  that  of  palm  nut, 
cocoanut,  olive,  hemp  seed,  linseed,  cotton  seed,  fish,  or  lard 
may  be  used,  and  fats  like  beef  tallow,  mutton  tallow,  lard, 
or  house  grease. 

The  process  of  "saponification"  may  be  brought  about 
either  by  the  action  of  water  or  steam  at  high  temperature 
and  pressure  (especially  in  the  presence  of  a  dilute  mineral 


SANITARY  AND   APPLIED   CHEMISTRY 

acid),  by  the  action  of  caustic  alkalies,  or  sometimes  by  the 
use  of  lime  (see  Candles,  p.  49). 

The  fats  may  be  briefly  described  as  consisting  of  ethers 
of  the  triatomic  alcohol-radicle,  containing  glycyl,  C3H5.  By 
treatment  with  alkalies  or  high-pressure  steam,  they  yield 
gylcyl  alcohol  (glycerin)  and  stearic  or  other  fatty  acid.1 

The  name  given  to  the  compound  of  the  acid  and 
glycerin  is  stearin,  palmitin,  or  olein.  In  the  case  of 
stearin,  the  saponification  equation  would  be:  — 

C8H5(C18H3A)s  +  3  KOH  =  C3H8(OH)3  +  3  KC^H^. 

Stearin  Caustic  Potash  Glycerin  Soap 

With  palmitin  or  olein,  the  reaction  is  similar.  If  the 
fat  or  oil  is  solid,  it  contains  a  preponderance  of  stearin  or 
palmitin,  but  if  liquid,  there  is  an  excess  of  olein. 

In  making  soap  on  a  large  scale,2  a  kettle,  provided  with 
both  a  closed  and  open  steam  coil,  so  that  the  soap  may  be 
boiled  either  by  the  heat  or  the  free  steam,  is  used.  A  ket- 
tle that  will  hold  100,000  Ib.  of  soap  is  15  ft.  in  di- 
ameter and  21  ft.  high,  and  is  made  of  f -in.  boiler  plate. 
The  melted  fat  and  lye  are  run  into  the  kettle  and  mixed 
by  the  aid  of  free  steam  and  boiled  for  some  time,  or  until 
the  soap  has  a  dry,  firm  feel  between  the  fingers ;  it  is  then 
"salted  out "  by  adding  common  salt.  In  boiling,  the  saponi- 
fication represented  in  the  above  equation  has  taken  place, 
and  when  salt  is  added  this  causes  the  soap  to  separate  from 
the  caustic  lye  and  glycerin.  After  boiling,  to  mix  thor- 
oughly, the  mass  is  allowed  to  stand  in  the  kettle  till  the 
soap  rises  to  the  top,  and  then  the  lye  may  be  drawn  off  at 
the  bottom  of  the  kettle.  Some  more  strong  lye  is  then 
added,  and  the  boiling  is  continued  till  the  material  is 
fully  saponified,  which  the  experienced  soap  boiler  knows 

1  Allen,  "  Commercial  Organic  Analysis,"  p.  183. 
8 Thorp, "Outlines  of  Industrial  Chemistry,"  p.  340. 


CLEANING  :     SOAP,   BLUING  99 

by  sight,  feel,  and  taste,  and  then  the  contents  of  the 
kettle  is  again  allowed  to  stand  for  a  while,  and  the  addi- 
tional lye  is  drawn  off.  The  soap  is  then  boiled  with  some 
water,  and  is  allowed  to  settle  again,  to  allow  the  separation 
of  more  alkali,  dirt  and  impurities,  called  "nigre."  After 
standing  several  days,  the  soap  is  pumped  into  the 
"crutcher,"  which  consists  of  a  broad,  vertical  screw  work- 
ing within  a  cylinder,  which  is  placed  in  a  larger  tank. 
Here  it  is  thoroughly  mixed,  and  any  perfume  or  scouring 
material  may  be  added.  The  soap  is  then  drawn  off  into 
rectangular  "frames,"  holding  about  1000  lb.,  where  it  is 
allowed  to  solidify.  The  sides  of  these  frames  are  re- 
moved and  the  soap  is  cut,  by  means  of  a  wire,  into  slabs 
and  then  into  bars.  If  put  on  the  market  in  the  form  of 
cakes,  the  bars  are  pressed  into  the  desired  shape. 

For  making  white  soaps,  tallow,  palm  oil,  and  cocoanut 
oil  are  used.  Castile  soap,  if  genuine,  is  made  from  olive  oil, 
sometimes  with  the  addition  of  cocoanut  or  rape  seed  oil. 
It  is  useless  to  attempt  to  make  a  good  soap  out  of  inferior 
material.  In  making  lower  grades  of  soap,  cheaper  fats  are 
used,  and  frequently  those  that  have  a  rancid  odor.  This  is 
sometimes  "corrected"  by  the  addition  of  a  strong  perfume, 
like  oil  of  "  mirbane," —  nitrobenzene,  made  from  coal  tar. 
Yellow  soaps  almost  always  contain  considerable  rosin;  that 
is,  they  are  made  by  the  usual  process,  except  that  quite  a 
large  proportion  of  rosin  is  used  to  replace  the  fat.  This 
has  valuable  soap-making  qualities,  and  would  not  be  classi- 
fied as  an  adulterant  of  soap.  Cocoanut  oil  saponifies  with- 
out boiling,  so  it  is  used  in  making  the  "cold  process"  soap. 
This  material  also  admits  of  the  use  of  a  larger  quantity  of 
water,  so  that  the  soap  will  be  hard  and  still  contain  as 
much  as  70  %  of  water.  Soap  is  mottled  by  stirring  into 
it,  while  warm,  some  coloring  substance,  such  as  copperas, 
ultramarine,  or  an  aniline  color. 


100  SANITARY  AND  APPLIED  CHBMI8TEY 

Sand  soap,  pumice  soap,  and  compounds  of  a  similar 
character  are  made  by  incorporating  sand  or  powdered  pum- 
ice, with  the  ground  soap,  and  this  ought  to  lessen  the 
price  of  the  soap  very  materially.  These  substances  can  act 
only  mechanically ;  that  is,  they  sandpaper  off  the  dirt.  A 
silicated  soap  is  made  by  mixing  with  the  ordinary  soap 
some  silicate  of  soda  or  soluble  glass,  as  it  is  called.  Into 
most  laundry  soaps  both  sodium  silicate  and  sodium  car- 
bonate are  "  crutched,"  as  a  filler  to  soften  hard  water  and 
to  give  additional  detergent  properties. 

Toilet  soap  is  made  either  by  melting  raw  soap,  by  per- 
fuming an  odorless  soap,  after  cutting  in  fine  shavings  and 
drying,  or  by  making  the  soap  directly  by  the  use  of  pure 
materials.  In  either  case  the  mass  is  colored  by  metallic 
oxides  or  aniline  colors,  and  is  perfumed  by  the  use  of 
essential  oils,  and  then  it  is  pressed  into  molds  while 
yet  fresh. 

To  make  a  transparent  soap  it  is  necessary  to  dissolve  an 
ordinary  soap  in  alcohol,  allow  the  insoluble  residue  to 
settle  out,  and  distill  the  alcoholic  solution  to  jelly.  This 
may  then  be  pressed  into  molds  and  dried.  Another 
method  very  frequently  employed  is  to  make  a  cold  process 
soap,  with  coloring  matter  and  perfume  added,  and  then  to 
add  to  the  mass  more  glycerin,  or  a  strong  sugar  solution, 
which  renders  it  still  more  transparent. 

Soft  soap  is  made  directly  by  the  use  of  potash  lye,  or  by 
the  use  of  soda  lye  and  considerable  water.  The  glycerin 
and  the  excess  of  lye,  if  any,  remain  in  the  soft  soap.  This 
is  used  in  "fulling"  or  shrinking  cloth  and  in  other  manu- 
facturing operations,  probably  on  account  of  the  excess 
of  alkali  which  it  contains. 

The  salt  lye  which  is  drawn  off  from  the  kettle  in  which 
soap  is  boiled  is  used  for  the  manufacture  of  glycerin.  In 
this  process  the  soluble  soap  and  impurities  are  taken  out 


CLEANING:  SOAP,  BLUING  101 

by  chemical  treatment,  and  mineral  salts  are  separated 
by  evaporation  and  crystallization.  The  purified  crude 
residue  containing  about  80  %  glycerin  is  distilled  with 
steam  under  diminished  pressure. 

It  is  not  economy  to  use  a  cheap  soap,  as  on  account  of 
the  excess  of  alkali  which  it  usually  contains  it  injures  the 
fabrics  washed,  by  causing  the  fibers  to  disintegrate  and 
readily  fall  apart. 

There  is  a  great  advantage  in  using  a  well-dried  soap, 
as  it  does  not  so  readily  become  soft  in  the  water  and  there- 
fore does  not  wash  away  so  qxiickly.  A  laundry  soap 
will  lose  25  %  of  water  if  the  bars  are  piled  and  allowed 
to  remain  for  some  time  where  they  are  freely  exposed  to 
the  air. 

In  his  researches  on  soap,  Chevreul  said  that  the  cleaning 
action  was  because  the  soap  was  decomposed,  when  brought 
in  contact  with  water,  into  fatty  acid  and  alkali.  The 
impurities  are  set  free  by  the  alkali  and  entangled  by  the 
fat  acid  salts,  and  thus  removed  with  the  lather.  Thus  it 
will  be  seen  that  vigorous  rubbing  is  not  necessary  to  remove 
the  dirt,  though,  of  course,  it  aids  the  process. 

Ordinary  soaps  are  readily  soluble  in  water,  but  if  the 
water  is  "  hard "  from  the  presence  of  lime  or  similar 
mineral  substances,  the  alkali  soap  is  decomposed  and  an 
insoluble  lime  soap  is  precipitated,  thus  forming  a  dis- 
agreeable scum  on  the  water.  Not  until  all  this  lime  is 
thrown  down  by  the  soap  will  the  latter  begin  to  have  a 
detergent  action. 

The  equation  for  the  formation  of  the  lime  soap  would 
be:  — 

2C1»H<B0,Na  +  CaS04  =  CaCCuHjA).  +  Na^SO* 

On  account  of  the  necessity  for  using  hard  water  in  some 
localities  "washing  soda"  NaaCOs  +  10  H20  is  used  to 


102  SANITARY   AND   APPLIED   CHEMISTRY 

"break"  the  wafer;  that  is,  to  precipitate  the  lime  so  that 
less  soap  will  be  required,  thus  :  — 

CaH2(C03)2  +  Na2C03  =  CaCO8  +  2NaHC03. 

(See  Hard  water,  p.  67.) 

In  order  to  make  a  laundry  soap  fit  for  hard  water,  sodium 
carbonate  is  added  to  it  in  the  crutching. 

Experiment  56.  To  make  a  hard  soap,  dissolve  in  a 
medium-sized  beaker  15  grama  of  caustic  soda  (sticks)  in 
120  cc.  of  water,  and  pour  one  half  of  this  into  a  porcelain 
evaporating  dish  of  at  least  500  cc.  capacity,  add  60  cc.  of 
water  and  50  grams  of  tallow.  Boil  this  solution  for  three 
quarters  of  an  hour,  carefully  replacing,  from  time  to  time, 
the  water  that  has  been  lost  by  evaporation ;  then  add  the 
remainder  of  the  solution  of  caustic  soda  and  boil  for  at 
least  an  hour  more.  Water  should  be  added  as  before,  but 
the  volume  of  the  liquid  may  be  allowed  to  decrease  about 
one  third.  Add  20  grams  of  salt,  boil  for  a  few  minutes, 
and  allow  the  liquid  to  cool.  The  soap  will  rise  to  the  top, 
and  the  glycerin,  excess  of  lye,  and  salt  will  remain  in 
solution. 

Experiment  57.  Slightly  acidify  the  water  solution  sepa- 
rated from  the  soap  in  the  above  experiment  with  dilute 
hydrochloric  acid.  If  any  fatty  acids  or  impurities  separate 
out,  filter.  Pour  the  solution  into  a  porcelain  evaporating 
dish,  and  evaporate  to  dryness  on  a  water  bath.  Dissolve 
the  residue  in  strong  alcohol,  filter  or  decant  from  the  un- 
dissolved  crystals  of  salt,  and  evaporate  the  alcohol.  The 
slight  residue  will  be  sticky,  and  give  the  sweet  taste  of 
glycerin. 

Experiment  58.  Cut  a  good  quality  of  soap  into  shavings 
and  mix  with  hot  water  on  a  water  bath,  until  well  dissolved. 
Add  dilute  sulfuric  acid  until  the  solution  is  acid.  Note 


CLEANING:     SOAP,   BLUING  103 

that  if  the  soap  is  "  filled,"  the  sodium  carbonate  will  cause 
an  effervescence  on  adding  acid.  Heat  on  the  water  bath  for 
some  time  or  boil  slowly,  and  the  fatty  acid  will  separate, 
forming  an  oily  layer  on  the  top.  When  clear  this  may  be 
separated  from  the  water  by  pouring  on  a  wet  filter,  and  the 
sulfuric  acid  removed  by  washing  on  the  filter  with  hot  water. 
Washing  soda,  Na2C0310H20,  is  often  used,  not  only 
to  soften  hard  water,  but  as  a  stronger  washing  agent 
than  soap.  This  is  a  much  better  material  than  most  of  the 
so-called  washing  powders  of  the  grocer.  It  should  always 
be  dissolved  in  a  bottle  or  other  vessel,  and  used  as  a  solu- 
tion in  the  quantities  necessary.  An  excess  disintegrates 
the  fabrics,  or  "rots  "the  goods.  Sometimes  the  washing 
powders  or  liquids  on  the  market  contain  in  addition  to  the 
washing  soda,  a  little  soap  or  ammonium  carbonate  or  a 
small  per  cent  of  borax,  but  they  are  much  more  expensive 
than  the  common  washing  soda,  and  no  more  efficient. 

Experiment  59.  To  test  a  washing  powder  for  sodium  car- 
bonate, put  a  little  of  it  in  a  test  tube  and  add  a  few  drops 
of  hydrochloric  acid.  If  there  is  a  brisk  effervescence,  it 
will  indicate  the  presence  of  a  carbonate,  and  if  the  gas  that 
is  given  off  colors  the  flame  of  a  Bunsen  burner  yellow,  it 
indicates  sodium. 

BLUING 

Bluing  is  the  process  resorted  to  in  the  laundry  to  over- 
come the  slight  yellow  color  of  the  clothes,  and  for  the 
same  purpose  in  the  bleacheries  where  new  goods  are  finished. 

Indigo  was  one  of  the  substances  most  commonly  used 
some  years  ago.  It  was  known  to  the  ancient  Egyptians  as 
a  dye  and  to  the  Komans  as  a  pigment.  The  method  of 
using  it  for  bluing,  as  it  is  insoluble  in  water,  is  to  tie  up 
a  lump  in  a  cloth,  and  when  soaked  in  water  the  finely 
divided  precipitate  which  is  in  suspension  will  give  a  blue 


104  SANITARY   AND   APPLIED   CHEMISTRY 

color  to  the  water,  and  to  the  clothes,  which  are  immersed 
in  it. 

Prussian  blue  (ferric  ferrocyanid),  Fe4(Fe(CN)6)3,  is  also 
used  for  bluing.  It  is  insoluble  in  water  and  in  mineral 
acids,  but  is  decomposed  by  alkalies  and  dissolved  by  oxalic 
acid.  It  is  generally  used  as  a  solution  or  "  liquid  blue,"  but 
this  imparts  to  the  goods  a  greenish  blue  color.  On  account 
of  the  ease  with  which  it  is  decomposed  by  alkalies,  there 
is  danger  that  "  iron  rust "  will  be  deposited  on  the  goods 
if  this  form  of  blue  is  used. 

^  Experiment  60.  Make  Prussian  blue  by  the  action  of 
ferric  chlorid,  FeCl3,  upon  potassium  ferrocyanid,  K4Fe(CN)6, 
in  the  presence  of  a  few  drops  of  hydrochloric  acid.  Treat 
this  blue  precipitate  with  an  excess  of  sodium  hydroxid, 
and  heat  to  boiling.  Notice  the  reddish  brown  precipitate 
of  ferric  hydrate,  Fe(OH)3. 

Experiment  61.  Make  some  Prussian  blue,  as  in  the  pre- 
vious experiment,  and  add  to  the  precipitate,  in  the  test 
tube,  a  few  crystals  of  oxalic  acid,  and  warm  the  mixture. 
Notice  the  intense  blue  solution  obtained  (liquid  blue). 

Ultramarine  is  an  interesting  artificial  compound  which 
is  put  upon  the  market  in  the  shape  of  small  "  bluing  balls." 
It  is  similar  to  the  native  mineral  called  "  lapis  lazuli,"  and 
is  a  double  silicate  of  sodium  and  aluminum  containing  sul- 
fur. Like  indigo,  it  is  insoluble  in  water  and  is  simply 
held  in  suspension  in  that  liquid.  There  is  difficulty  in 
preventing  the  formation  of  blue  spots  and  streaks  with 
the  solid  blue.  This  blue  is  extensively  used  for  coloring 
wall  paper  and  for  "  bluing  "  white  sugar. 

'"~  Experiment  62.  To  show  the  presence  of  sulfur  in  ultra- 
marine, place  a  part  of  a  bluing  ball  in  water  in  a  test  tube, 
and  add  to  it  enough  hydrochloric  acid  to  make  the  solution 
acid.  Notice  the  odor  of  escaping  gas  when  the  solution  is 


CLEANING  :    SOAP,   BLUING  105 

warmed,  and  test  it  for  hydrogen  sulfid,  by  holding  in 
the  gas  a  paper  dipped  in  lead  acetate  solution.  The  paper 
turns  black  on  account  of  the  formation  of  lead  sulfid. 

Aniline  colors  made  from  coal  tar  are  the  basis  of  most 
of  the  liquid  blues  on  the  market  at  the  present  time.  The 
soluble  blues  from  this  source  are  very  numerous,  and  they 
are  probably  as  satisfactory  as  anything  for  this  purpose. 


CHAPTER  IX 
DISINFECTANTS,   ANTISEPTICS,  AND  DEODORANTS 

SINCE  the  health  of  the  body  depends  so  largely  upon 
sanitary  surroundings,  it  is  important  to  consider  what 
assistance  modern  science  can  offer  to  bring  about  the  most 
hygienic  conditions  in  the  household.  Infection,  in  general 
terms,  is  something  capable  of  producing  disease  that  comes 
to  the  body  from  without,  and  this  infection  usually  reaches 
the  system  by  the  aid  of  certain  lower  forms  of  life  known 
as  microorganisms.  These  microorganisms  may  be  distrib- 
uted by  impure  water,  by  house  flies,  by  flying  dust,  or  by 
personal  contact  between  individuals.  We  may  try  to  check 
the  progress  of  a  disease  within  the  body,  where  it  becomes  a 
very  difficult  problem,  or,  what  is  better,  the  attempt  may  be 
made  to  prevent  the  disease  from  invading  the  body  by  keep- 
ing the  dangerous  microbes  out,  or  destroying  them  before 
they  have  an  opportunity  to  enter  it.  Those  substances  which 
are  capable  of  checking  the  growth  of  the  microorganisms, 
but  without  necessarily  killing  them,  are  known  as  "anti- 
septics"; so  all  "disinfectants,"  or  destroyers  of  infection, 
are  also  antiseptics,  but  antiseptics  are  not  necessarily 
disinfectants.  (The  surgeon  of  to-day  deals  with  wounds  in 
such  a  way  as  to  have  the  conditions  aseptic, — that  is,  to 
have  all  germs  excluded  in  the  operation, — which  is  far 
better  than  attempting  to  destroy  them  when  once  intro- 
duced into  the  wound.)  1 

1  Sedgwick,  "  Principles  of  Sanitary  Science  and  the  Public  Health," 
pp.  326,  327. 

106 


DISINFECTANTS,   ANTISEPTICS,   AND   DEODORANTS     107 

Those  substances  that  destroy  foul  odors  are  often  called 
disinfectants.  This  may  be  true  or  it  may  not.  Some 
things  destroy  foul  odors,  or,  in  fact,  simply  cover  them  up 
without  in  the  least  going  to  the  source  of  the  trouble,  and 
they  are  not  disinfectants  but  simply  "odor  killers."  The 
American  Public  Health  Association's  committee  defines 
a  disinfectant  as,  "An  agent  capable  of  destroying  the 
infective  power  of  infectious  material."  This  does  not, 
however,  represent  the  popular  view  of  the  subject.  Deo- 
dorants, though  they  may  be  of  great  value  in  their  place, 
are  not  disinfectants  or  antiseptics. 

Many  people  are  in  the  habit  of  relying  on  the  sense  of 
smell  to  prove  the  presence  of  injurious  as  well  as  dis- 
agreeable substances  in  the  air.  The  nose  is,  no  doubt,  an 
excellent  watchman  to  protect  the  body,  but  whether  we 
destroy  a  foul  odor  or  simply  overcome  it  by  a  more  pungent 
one  is  not  for  the  sense  of  smell  to  distinguish,  for  germs 
that  render  the  air  poisonous  are  not  necessarily  destroyed 
when  no  vile  odor  can  be  perceived.  Because  a  substance 
is  put  on  the  market  as  a  "microbe  killer"  or  a  "perfect 
disinfectant,"  it  is  not  a  proof  that  it  is  of  any  value,  any 
more  than  the  fact  that  a  patent  medicine  is  advertised  as  a 
specific  for  all  the  ills  of  the  flesh  is  a  proof  that  it  will 
have  that  effect. 

TESTS   FOR   DISINFECTION 

These  tests  may  be  of  three  kinds : l  — 

First.  From  the  practical  experience  of  those  engaged  in 
sanitary  work.  Such  diseases  as  smallpox,  diphtheria,  and 
scarlet  fever  have  in  many  instances  been  contracted  after 
months,  from  the  use  of  clothing  that  has  been  about  a 
patient,  or  from  the  occupancy  of  rooms  where  he  has  been 

1  Dr.  Sternberg,  American  Public  Health  Association. 


108  SANITARY   AND   APPLIED   CHEMISTRY 

sick.  (Books  that  have  been  in  the  sick  room  have  commu- 
nicated disease  months  after  they  were  removed  from  the 
room.)  If,  after  an  attack  of  the  disease,  the  rooms  have 
been  thoroughly  disinfected,  the  disease  has  been  completely 
stamped  out  in  that  place. 

Second.  Inoculation  experiments  have  been  made  upon 
animals  with  infected  material,  and  with  the  same  material 
that  had  previously  been  subjected  to  the  action  of  disin- 
fectants. In  the  former  case  the  disease  was  transmitted, 
and  in  the  latter  it  was  not,  and  thus  the  efficiency  of  the 
disinfectant  was  shown.  It  is  known  that  in  many  infec- 
tious diseases  the  infecting  agent  is  a  germ,  and  in  these 
cases  the  effect  of  disinfection  is  to  destroy  the  germ. 
Experiments  have  been  tried  upon  man  with  disinfected 
vaccine  virus,  and  with  the  same  virus  that  has  not  been 
thus  treated,  and  the  vaccination  with  the  first  was  not 
successful  while  that  with  the  latter  was.  In  this  way  the 
efficiency  of  a  disinfectant  was  shown. 

Third.  Experiments  are  made  directly  on  the  disease 
germs,  culture  experiments  as  they  are  called.  Here  the 
germs  are  allowed  to  propagate  in  such  fluids  as  extract  of 
beef,  or  bouillon,  and  thus  it  is  possible  to  study  the  life- 
history  of  these  germs  outside  the  body,  and  to  learn  what 
agents  are  efficient  in  destroying  them. 

Some  bacteria  multiply  by  "division"  and  others  by 
"spores"  also,  and  the  latter  are  more  difficult  to  destroy, 
because  the  organism  is  at  that  time  in  what  may  be  called 
a  resting  stage.  Often  it  is  possible  to  prevent  the  growth 
and  development  of  germs  by  the  use  of  antiseptics  or  dis- 
infectants; the  germs  are  not  destroyed,  but  the  disease 
is  arrested. 

"An  ideal  disinfectant  is  one  which,  while  capable  of 
destroying  the  germs  of  disease,  does  not  injure  the  bodies 
and  material  upon  which  the  germs  may  be  found ;  it  must 


DISINFECTANTS,    ANTISEPTICS,   AND   DEODORANTS      109 

also  be  penetrating,  harmless  in  handling,  inexpensive,  and 
reliable.1  This  ideal  disinfectant  has  not  yet  been  discov- 
ered." There  are,  however,  some  inexpensive  and  common 
substances  which  can  be  used  to  destroy  the  germs  of 
disease  with  good  effect.  Among  the  substances  used  as  disin- 
fectant and  antiseptic  agents,  the  following  may  be  noted:  — 

Sunlight  is  an  excellent  disinfectant,  if  the  material  can 
be  exposed  to  the  direct  rays  of  the  sun.  It  has  been  shown 
that  the  bacillus  of  tuberculosis  is  killed  by  direct  sunlight, 
and  that  of  typhoid  fever  also  under  certain  conditions. 
Even  diffused  light  is  of  value  as  an  adjunct  to  the  other 
methods  for  the  destruction  of  germs,  so  there  is  reason  in 
the  common  practice  of  "airing"  bedrooms,  and  letting  in 
all  the  sunlight  possible  for  a  time  every  day. 

Dry  air  is  an  excellent  purifier,  especially  if  accompanied 
by  sunlight,  chiefly  on  account  of  the  large  number  of 
oxidizing  bacteria  which  are  present.  It  will  remove 
moisture  and  often  prevent  decomposition  in  this  way, 
for  moisture  is  usually  the  friend  of  disease  and  decay. 

Dry  earth  also  allows  oxidation  and  arrests  foul  odors. 
This  fact  is  utilized  in  the  dry  earth  closet. 

Charcoal,  especially  that  made  from  bones,  is  an  excellent 
deodorizer  and  will  remove  foul  odors  quite  readily.  A 
handful  of  boneblack  sprinkled  on  a  piece  of  putrefying 
flesh  will,  after  a  short  time,  prevent  any  foul  odors  from 
escaping  from  it.  Wood  charcoal  acts  less  effectively  in  the 
same  way,  but  on  account  of  its  porosity  absorbs  gases 
very  quickly. 

Experiment  63.  Into  a  bottle  containing  200  cc.  of 
dilute  hydrogen  sulfid  water,  which  has  the  character- 
istic odor,  put  about  30  grams  of  boneblack  and  shake  for 
some  time.  Filter,  and,  if  the  conditions  have  been  care- 

1  Price,  "  Handbook  of  Sanitation,"  p.  223. 


110  SANITARY   AND   APPLIED   CHEMISTRY 

fully  observed,  the  filtrate  will  have  no  odor  of  hydrogen 
sulfid  gas,  as  it  will  have  been  absorbed  by  the  animal  charcoal. 

Quicklime  is  also  used  for  purposes  of  disinfection.  On 
account  of  its  cheapness,  "  milk  of  lime,"  Ca(OH)2,  is  recom- 
mended, especially  in  camp  sanitation,  for  destroying  foul 
organic  matter.  Some  physicians  regard  it  as  efficient  as 
chlorid  of  lime. 

A  variety  of  substances  are  used  to  cover  up  vile  odors, 
while  they  do  not  pretend  to  destroy  them.  The  bad  smells 
in  the  house  may  be  overcome  by  burning  sugar,  cotton  clofch, 
or  coffee.  (The  lack  of  personal  cleanliness  may  be  made 
less  noticeable  by  the  free  use  of  perfumes,  but  this  is  a 
method  belonging  to  an  earlier  kind  of  civilization  rather 
than  to  our  own.) 

More  effective  than  any  of  the  methods  above  noticed  are 
the  following  —  in  the  absence  of  spores :  — 

Heat,  at  a  temperature  of  302°  F.  (150°  C.),  may  be  used  for 
disinfecting,  and  should  be  continued  for  at  least  two  hours. 
A  higher  temperature,  continued  for  a  shorter  time,  will 
also  destroy  the  bacteria.  Sometimes  clothing  that  would  be 
injured  by  moist  heat  may  be  treated  in  this  way.  The 
goods  may  be  heated  in  an  oven,  but  should  not  be  folded 
or  piled  close  together.  This  method  has  been  used  for  dis- 
infecting by  boards  of  health  in  large  cities,  but  it  is  inferior 
to  steam  at  the  same  temperature,  and  does  not  penetrate 
as  well. 

Sulfur  dioxid,  made  by  the  burning  of  sulfur,  is  one 
of  the  oldest  agents  used  for  disinfection.  A  convenient 
way  in  which  to  use  this  is  to  put  several  pounds  of  sulfur 
in  an  iron  kettle,  and  to  place  that  on  bricks  in  a  pan  of 
water.  Then  light  the  sulfur  by  means  of  burning  coals, 
or  alcohol,  and  close  the  room  very  tightly.  Five  pounds 
is  considered  a  sufficient  quantity  for  a  room  containing 
1000  cu.  ft.  of  space.  Sometimes  a  solution  of  sulfur 


DISINFECTANTS,   ANTISEPTICS,   AND   DEODORANTS     111 

dioxid  is  simply  exposed  to  the  air  of  the  room.  Ten 
pounds  of  the  liquid  would  be  necessary  for  1000  cu.  ft. 
of  space.  The  presence  of  moisture  in  the  room  or  on  the 
goods  greatly  assists  the  operation.  The  more  tightly  the 
room  is  closed,  by  pasting  strips  of  paper  over  the  cracks 
beside  the  doors  and  windows,  the  better  the  disinfection 
will  be  accomplished,  and  this  precaution  should  not  be 
neglected.  Clothing  and  bedding  should  be  opened  out  as 
much  as  possible,  so  as  to  bring  it  in  contact  with  the  S02 
gas,  and  the  room  should  remain  closed  at  least  24  hours. 
This  gas  is  liable  to  bleach  certain  colors,  so  it  should  not 
be  used  with  colored  fabrics.  Liquid  sulfur  dioxid,  con- 
tained in  strong  steel  cylinders,  can  now  be  obtained  in  the 
market.  It  is  extremely  convenient  to  use  for  disinfection 
as  it  is  only  necessary  to  open  the  valve  and  allow  the  gas 
to  fill  the  room.  Sulfur  dioxid  is,  after  all,  only  a  surface 
disinfectant,  and  is  said  to  be  effective  only  against  a 
limited  number  of  pathogenic  bacteria. 

Carbolic  acid,  C6H5OH,  is  an  agent  that  has  often  been 
overrated,  on  account  of  its  penetrating  odor,  and  because  a 
small  quantity  will  overcome  most  other  odors.  This  acid 
of  a  strength  of  1  to  15,000  will  prevent  decomposition,  but 
1  to  1000  will  be  needed  to  destroy  spores.1  It  is  an  excellent 
substance  to  use  for  washing  floors,  walls,  etc.,  and  for 
disinfecting  soiled  clothing  and  discharges,  as  its  antiseptic 
power  is  great.  Although  not  very  soluble  in  water,  a  con- 
venient solution  can  be  made  by  adding  it  to  water  till  the 
latter  becomes  saturated,  about  1  to  20,  or  the  solubility  can 
be  increased  by  the  addition  of  glycerin. 

The  cresols,  which  are  found  in  commercial  carbolic  acid, 
and  are  powerful  germicides,  are  constituents  of  many  of 
the  disinfecting  solutions  now  on  the  market,  and  they  are 
believed  by  some  to  be  superior  to  carbolic  acid. 

1  Price,  "Handbook  of  Sanitation,"  p.  252. 


112  SANITARY   AND   APPLIED   CHEMISTRY 

Copper  sulfate,  CuS045H20,  or  "blue  vitriol,"  of  about 
10  %  strength,  is  to  be  recommended,  on  account  of  its 
comparative  cheapness,  especially  as  a  deodorant.  It  forms 
a  blue  solution,  with  water,  and  is  very  soluble  in  that  agent. 

Iron  sulfate,  FeS047H20,  or  the  "copperas"  of  com- 
merce, is  very  efficient  for  certain  purposes.  In  the  propor- 
tion of  2  Ib.  to  a  gallon  of  water,  it  may  be  used  with 
great  convenience  and  success  to  purify  sink  drains  and 
cesspools.  It  may  also  be  sprinkled  in  places  where  there 
are  foul  odors  from  the  decay  of  organic  matter,  and  they 
will  be  completely  overcome. 

Zinc  chloride,  ZnCl2,  is  very  largely  used  as  a  disinfectant 
and  a  deodorant.  As  its  solution,  as  well  as  that  of  zinc 
sulfate,  is  colorless,  it  will  not  stain  the  most  delicate  fab- 
rics, so  it  can  be  used  on  any  clothing  that  is  not  injured 
by  washing.  A  5  %  or  10  %  solution  may  be  used  for  this 
purpose  or  for  destroying  foul  odors. 

Potassium  permanganate,  KMn04,  since  it  is  a  strong  oxi- 
dizing agent,  may  be  used  as  a  germicide  in  some  cases, 
but  is  rather  expensive.  The  use  of  this  material  in  the 
purification  of  cistern  waters  has  already  been  suggested 
(p.  73). 

Hydrogen  peroxid,  H202,  is  now  a  commercial  article, 
and  its  aqueous  solution  is  sold  at  a  reasonable  price. 
There  are  some  cases  where  this  mild  disinfectant  may  be 
applied  with  success,  as  it  will  destroy  the  bacillus  of  ty- 
phoid fever,  cholera,  and  diphtheria  quite  readily. 

There  are,  however,  more  efficient  agents  in  disinfection 
than  those  that  have  been  mentioned,  because  under  the 
proper  conditions  they  are  of  sufficient  power  to  destroy  the 
spores  of  disease. 

Fire,  it  is  well  known,  is  effective  to  wipe  out  the  disease 
germs.  Old  clothing  and  bedding  would  better  be  burned 
than  that  an  attempt  should  be  made  to  disinfect  it.  The 


DISINFECTANTS,   ANTISEPTICS,   AND   DEODORANTS     113 

great  fire  of  London,  that  followed  the  plague,  no  doubt  was 
a  blessing,  in  that  it  actually  destroyed  the  last  traces  of  the 
disease.  That  was  more  important  in  those  days  than  it 
would  be  now,  for  they  did  not  know  the  first  principles  of 
the  science  of  disinfection. 

Steam  heat  is  one  of  the  most  valuable  physical  agents 
for  the  destruction  of  germs,  as  it  kills  bacteria  at  once,  and 
spores  after  a  short  time.  It  is  especially  valuable  for  the 
disinfection  of  clothing,  textile  fabrics,  carpets,  etc.,  as  it  is 
very  penetrating.  Municipal  authorities  are  making  use  of 
this  method  of  disinfection  on  a  large  scale  with  great  suc- 
cess. If  it  seems  desirable,  the  material  can  be  subjected 
to  quite  a  high  temperature  by  the  use  of  superheated  steam. 
In  some  communities  machines  mounted  on  wheels  are 
used.  A  large  apparatus  has  been  introduced  which  is  so 
constructed  that  the  mattresses,  bedding,  etc.,  may  be  intro- 
duced into  a  chamber,  from  which  the  air  is  exhausted 
by  means  of  a  steam  jet.  Dry  steam  is  then  allowed  to 
enter,  and  a  temperature  of  230°  to  240°  F.  is  maintained  for 
15  m.,  after  which  the  steam  exhauster  again  produces  a 
practical  vacuum,  and  finally  air  is  drawn  through  the 
chamber,  and  the  dried  materials  may  be  removed.  An 
apparatus  of  this  character  is  used  at  the  New  York  Quar- 
antine Station. 

Boiling  water  is  one  of  the  most  satisfactory  materials  to 
use  for  disinfecting  purposes.  There  are  very  few  germs 
that  can  withstand  a  boiling  temperature  for  half  an  hour. 
A  temperature  of  70°  G.  will  be  sufficient  to  kill  the  germs 
of  cholera,  tuberculosis,  diphtheria,  etc.  Hot  water  is  spe- 
cially applicable  to  textile  fabrics. 

Calcium  hypochlorite,  CaOCl2,  chlorid  of  lime,  or  "bleach- 
ing powder,"  is  a  convenient  disinfectant  to  use  in  some  cases. 
The  chlorid  of  lime  holds  the  chlorin  in  combination  very 
feebly,  so  that  the  smell  of  chlorin  is  always  apparent  in 


114  SANITARY   AND   APPLIED   CHEMISTRY 

a  good  sample.  The  fresh  sample  should  contain  from  30 
to  36  %  of  available  chlorin,  but  if  it  is  exposed  to  the 
air  for  a  time  it  loses  all  its  chlorin,  so  it  must  be  kept 
in  a  sealed  package  till  used.  Calcium  hypochlorite,  the 
efficient  substance  in  the  bleaching  powder,  is  soluble  in 
water,  but  the  solution  loses  its  strength  if  not  closely 
corked.  It  is  decomposed  when  brought  in  contact  with 
organic  matter,  and  very  effectually  kills  the  germs  of 
disease.  Experiments  with  chlorid  of  lime  as  a  disinfect- 
ant were  begun  as  early  as  1881,  by  Koch.  They  have 
been  continued  by  Sternberg,  Jaeger,  Nissen,  Klein,  Duggan, 
and  others,  and  all  showed  the  very  efficient  character  of 
this  substance  as  a  true  germicide.  Chlorid  of  lime  is 
convenient  to  sprinkle  about  in  the  vicinity  of  bad  odors, 
but  the  odor  of  the  chlorin  gas  given  off  is  disagreeable  and 
in  considerable  quantities  poisonous,  and  furthermore  it  has 
a  very  destructive  action  on  metals,  so  it  must  be  used 
with  discretion. 

Formaldehyde  gas,  HCHO,  or  "formalin,"  which  is  a 
40  °/0  solution  of  the  gas,  is  one  of  the  recent  disinfectants 
of  great  merit.  It  first  came  into  general  use  in  1892.  As 
it  is  a  good  germicide,  has  no  injurious  effect  on  fabrics  and 
colors,  and  can  be  readily  applied,  it  is  taking  the  place  of 
sulfur  dioxid  gas. 

There  are  several  ways  of  applying  the  gas :  A  polym- 
erized formaldehyde,  known  as  "paraform,"  is  sold  in 
pastilles,  which  when  heated  give  off  formaldehyde  gas ;  2 
oz.  of  paraform  for  1000  cu.  ft.  of  space,  with  an  ex- 
posure of  12  hr.,  is  recommended.  A  large  number  of  lamps 
have  been  devised  for  vaporizing  the  liquid  formalin  or  the 
paraform.  Another  method  of  generating  the  gas  is  to  use 
"  baignetti, "  which  contain  a  core  consisting  of  50  grams  of 
paraform.  As  the  baignette  burns  slowly  the  paraform  is 
volatilized  to  formaldehyde.  The  objects  to  be  disinfected 


DISINFECTANTS,   ANTISEPTICS,   AND  DEODOBANTS     115 

may  be  sprinkled  with  formalin,  and  inclosed  in  a  tight 
box,  so  that  they  may  be  subjected  to  the  vapor  for 
several  hours.  Another  method  is  to  wet  sheets  with  the 
solution  and  hang  them  in  the  room,  which  is  tightly 
closed,  for  some  time.  Still  another  method,  which  may  be 
used  on  a  large  scale,  is  to  vaporize  the  formaldehyde  gas 
in  a  retort  outside  the  room,  and  force  it  through  an  opening 
into  the  tightly  closed  space. 

Mercuric  chlorid,  HgCl2,  or  "corrosive  sublimate," 
which  stands  probably  at  the  head  of  all  substances  used  as 
disinfectants  and  antiseptics,  is  a  deadly  poison.  In 
solutions  of  1 : 15,000  it  stops  decomposition,  and  a  1 : 2000 
solution  will  kill  most  bacteria  in  two  hours.  If  of 
1 : 500  strength,  it  will  act  very  quickly  on  bacteria  and 
spores.  It  was  said  by  Koch  to  exercise  a  restraining  in- 
fluence on  the  development  of  the  spores  of  anthrax  bacillus, 
even  when  present  in  the  proportion  of  1 : 300,000,  but 
recent  experiments  show  that  its  germicidal  power  was 
overrated.  It  is  of  importance  to  note,  however,  that 
mercuric  chlorid  is  not  very  efficient  where  there  is  much 
albuminous  material,  because  it  so  readily  forms  with  the 
latter  an  insoluble  substance. 

If  a  wound  is  produced  by  a  rusty  nail  or  by  any  blunt 
instrument,  so  that  the  flesh  is  lacerated,  it  should  be 
opened  as  well  as  possible,  and  cleansed  with  warm 
water  and  then  filled  completely  with  a  solution  of  corrosive 
sublimate  (1  to  1000),  or  a  solution  of  carbolic  acid  of  5% 
strength  should  be  injected  to  destroy  any  dangerous  bac- 
teria that  may  be  present. 

Dr.  Sternberg  recommends  the  following  as  a  convenient 
solution  of  corrosive  sublimate  for  general  use:  — 

Mercury  bichlorid 1  oz. 

Copper  sulfate 1  lb. 

Water 1  gal. 


116  SANITARY   AND   APPLIED   CHEMISTRY 

The  advantage  of  this  solution  is  that  we  not  only  mix 
with  the  chlorid  of  mercury  a  valuable  disinfectant,  but 
the  solution  is  colored  blue,  and  so  it  is  less  liable  to  be 
used  accidentally.  It  should  be  marked  "  Poison." 


PAET   II 

CHEMISTRY  OF  FOOD 

CHAPTER  X 

USE  OF  FOODS 

IN  the  consideration  of  so  broad  a  subject  as  food,  there 
is  difficulty  at  the  outset  in  giving  it  a  satisfactory  defini- 
tion. The  growth  and  repair  of  the  body,  as  well  as  the 
potential  energy  by  virtue  of  which  the  body  is  able  to  do 
actual  work,  need  to  be  taken  into  account.  Food  has  been 
defined  as,  "Anything  which,  when  taken  into  the  body, 
is  capable  either  of  repairing  its  waste  or  of  furnishing  it 
with  material  from  which  to  produce  heat  or  nervous  and 
muscular  work."  l  It  is  important  to  distinguish  between 
food  and  medicine,  and  to  notice  that  the  latter  may  revive 
some  vital  action  but  will  not  supply  the  material  which 
sustains  that  action.  There  are,  however,  many  articles  of 
diet,  such  as  tea  and  coffee,  and  the  food  accessories,  such 
as  spices  and  condiments,  which,  although  they  do  not 
strictly  come  within  the  above  definition,  are  often  useful 
to  stimulate  the  appetite  or  to  make  the  food  more  agreeable. 

It  is  by  no  means  essential  that  a  single  food  should  con- 
tain all  the  nutrients  needed  by  the  body,  and  in  fact  it  is 
desirable  that  there  should  be  a  variety  of  food  to  stimulate 
the  appetite  and  vary  the  character  of  the  work  which  the 
organs  of  digestion  are  called  upon  to  perform.  Food  may 
contain  substances  which  must  be  broken  up  or  decom- 

1  Hutchison,  "  Food  and  Dietetics,"  p.  1. 
117 


118 


SANITARY   AND   APPLIED   CHEMISTRY 


posed  by  the  body  before  it  is  of  value,  or  it  may  contain 
substances  which  can  immediately  be  taken  into  the  circu- 
lation and  utilized. 

Some  food  is  of  use  because  it  furnishes  nearly  all  the 
nutritious  substances  needed  by  the  body,  while  other  foods 
furnish  some  special  material  in  an  economical  or  agreeable 
form.  Some  act  readily  in  sustaining  the  body,  or  are  easily 
digested ;  others  are  economical  and  offer  a  maximum  amount 
of  nourishment  at  a  minimum  cost. 

Not  only  does  food  sustain  the  body,  but  there  is  a  pro- 
vision of  nature  that  animals  should  derive  great  pleasure 
and  satisfaction  from  eating,  and  this  pleasure  is  due  to 
both  the  sense  of  smell  and  that  of  taste;  it  is  difficult  to 
consider  the  function  of  one  without  that  of  the  other. 

Since  these  senses  have  not  been  cultivated  as  highly  as 
the  others,  there  is  much  room  for  further  development;  but 
there  are  some  trades,  such  as  that  of  the  tea  taster,  the 
wine  sampler,  and  the  perfumer,  where  they  are  cultivated 
and  utilized.  The  student  of  physiology  finds  it  difficult 
to  classify  the  sense  of  taste  and  smell,  but  it  is  possible  to 
test  the  relative  delicacy  of  these  senses  for  various  sub- 
stances in  different  individuals.  Some  experiments  1  made 
by  the  author  for  the  delicacy  of  the  sense  of  taste,  with  a 
number  of  persons  of  both  sexes,  showed  that  it  was  possible 
to  detect  — 


BY  MALES 
(1  part  in) 

BY  FEMALKS 
(1  part  in) 

1    Bitter  substance  (quinine)  

392,000 

456  000 

2    Acid  substance  (sulfuric  acid)  .... 

2080 

3280 

3    Salt  substance  (sodium  chlorid)    .     .     . 

2240 

1980 

4    Sweet  substance  (cane  sugar)  .... 

199 

204 

6    Alkali  substance  (baking  soda)     .     .     . 

98 

126 

1  Science,  Vol.  XI,  p.  145. 


USE   OF   FOODS  119 

This  showed  that  the  sense  of  taste  for  bitter  substances 
was  far  more  delicate  than  for  other  classes,  and  that,  ex- 
cept in  the  case  of  salt,  the  females  could  detect  smaller 
quantities  than  the  males.  A  separate  set  of  tests  made 
upon  the  pupils  in  a  large  Indian  school l  showed  the  same 
order  of  delicacy. 

The  knowledge  that  man  has  obtained  as  to  which  foods 
are  wholesome  and  which  are  poisonous  is  largely  the  result 
of  experience,  and  this  experience  was  transmitted  and  grew 
from  one  generation  to  the  next.  Much  is  due,  then,  to  our 
ancestors,  who  have  had  the  courage  to  explore  in  the  realm 
of  untasted  food.  Even  now,  fatal  mistakes  in  the  selection 
of  food  are  sometimes  made,  and  children  must  in  every 
generation  be  warned  against  brilliantly  colored  berries. 

In  the  early  ages  the  variety  of  food  was  not  as  great  as 
now,  for  the  people  not  only  had  less  skill  in  preparing  and 
less  experience  in  selecting  food,  but  they  were  obliged  to 
depend  on  the  chase,  or  to  use  only  that  food  which  was  ob- 
tained in  the  immediate  vicinity  of  their  dwellings.  They 
were  not  able  to  draw  on  all  climates  as  we  do,  nor  could 
they  preserve  the  fruits  of  one  season  to  consume  in  another. 
Grain  was  stored,  fruits  were  dried,  and  meats  were  salted 
or  dried,  but  beyond  this  little  was  done  to  preserve  food. 

A  mixed  diet,  then,  may  be  considered  as  evidence  of  ad- 
vancing civilization.  The  palate  becomes  surfeited  with  too 
much  of  one  kind  of  food,  and  so  a  change  is  welcome 
to  stimulate  the  appetite.  A  monotonous  diet  is  often 
a  matter  of  necessity,  but  as  soon  as  man  has  the  oppor- 
tunity to  indulge  in  a  mixed  diet  he  is  not  slow  to  take  ad- 
vantage of  it.  With  increased  civilization  the  diet  becomes 
more  mixed  in  character,  and  on  this  account  it  does  not 
interfere  with  the  health  to  move  from  one  locality  or  cli- 
mate to  another. 

1  Rons.  Univ.  Quarterly,  Vol.  II,  p.  96. 


120  SANITARY  AND  APPLIED  CHEMISTRY 

There  is  no  doubt  that  man,  as  well  as  the  lower  animals, 
is  benefited  by  a  variety  in  food.  It  has  been  stated  that 
"digestion  experiments  made  with  one  kind  of  food 
material  do  not  give  on  the  whole  as  valuable  results  as 
those  in  which  two  or  more  food  materials  are  used.  In 
other  words,  it  appears  that  with  a  mixed  diet  the  same 
person  will  digest  a  larger  proportion  of  nutriment  than 
with  a  diet  composed  of  a  single  food  material."  It  is, 
of  course,  admitted  that  a  mixed  diet  may  present  greater 
temptations  to  overindulgence  in  food. 

It  stands  to  reason  that  as  some  foods  are  too  rich  in 
proteids  and  others  contain  too  large  a  proportion  of  carbo- 
hydrates, we  should  mix  these  in  the  proper  quantities. 
This  we  do  when  we  eat  "bread  and  cheese,"  potatoes  and 
beef,  or  rice,  eggs,  and  milk  in  puddings. 

As  the  system  adapts  itself  to  a  certain  kind  of  food  and 
the  stomach  secretes  gastric  juice  sufficient  in  kind  and 
quantity  for  that  food,  it  is  not  advisable  after  being  ac- 
customed to  one  kind  of  diet  for  a  long  time  to  change  too 
suddenly  to  one  that  is  entirely  different,  for  indigestion  may 
result. 

The  food  selected  should  be  suited  to  the  habits,  age,  and 
employment  of  a  person.  A  sedentary  man  will  not  thrive 
on  a  diet  that  is  too  stimulating,  nor  one  engaged  in  active 
manual  labor  upon  starchy  foods  alone.  The  food  that  is 
readily  digested  by  an  adult  will  be  not  at  all  adapted  to 
the  use  of  a  young  child. 

There  seems  to  be  an  instinctive  selection  of  particular 
classes  of  foods  for  special  climates  —  the  Eskimo  eats 
large  quantities  of  whale  blubber  or  fats;  the  Congo  natives 
live  mostly  upon  the  plantain;  the  Polynesians  subsist 
almost  wholly  on  bread  fruit.  Even  in  the  temperate  zone 
we  find  that  less  meat  is  eaten  in  warm  weather. 

Food,  in  order  to  be  agreeable  and  wholesome,  is  usually 
cooked.  This  is  necessary, — 


USE   OP  FOODS  121 

First,  to  improve  its  appearance  and  to  make  it  more 
agreeable  to  the  eye  and  thus  more  appetizing. 

Second,  because  warm  food  is  often  more  agreeable  than 
cold. 

Third,  to  improve  the  flavor  and  develop  the  odor,  par- 
ticularly in  the  case  of  meats. 

Fourth,  in  order  to  destroy  any  parasites  or  micro- 
organisms that  may  be  contained  in  the  food. 

Fifth,  to  bring  about  certain  chemical  changes  in  the  food, 
that  the  better  adapt  it  to  digestion. 

Sixth,  to  soften  the  material  so  that  it  may  more  readily 
be  acted  upon  by  the  digestive  fluids. 

When  proteids,  such  as  meat  or  eggs,  are  acted  upon  by 
heat,  even  if  the  temperature  is  not  above  170°  F.,  they  are 
coagulated  and  made  more  solid,  but  they  are  not  so  tough, 
and  the  bundles  of  fibers  may  more  easily  be  torn  apart. 
When  starchy  food,  as  grains  or  potatoes,  is  cooked,  the 
granules  swell  up,  the  outer  cellulose  envelope  bursts,  and 
thus  after  mastication  the  digestive  ferments  have  an  oppor- 
tunity to  come  more  intimately  in  contact  with  the  starch. 
According  to  Sykes,  moist  heat,  even  below  185°  F.,  causes 
most  starch  grains  to  burst,  so  that  the  starch  is  said  to  be 
gelatinized.1 

Food  must  be  of  such  a  character  that  it  will  build  up  the 
tissue  of  the  body  and  supply  it  with  energy  for  doing 
work.  Incidentally  the  heat  of  the  body  is  kept  up  by  cell 
action,  or,  as  one  author  puts  it,  ."is  a  by-product"  of 
functional  activity.  It  is  not  necessary  nor  advisable, 
however,  that  all  the  food  taken  into  the  body  should  be 
positively  nutritious.  It  will  be  a  long  time  before  the 
dreams  of  those  who  propose  that  we  carry  concentrated, 
or  perhaps  "synthetic,"  foods  for  several  days'  rations  in 
the  vest  pocket  will  be  realized.  Not  only  would  such 
1  Hutchison,  "Food  and  Dietetics,"  p.  378. 


122  SANITAEY   AND   APPLIED   CHEMISTRY 

food  soon  become  positively  insipid  and  disagreeable,  but 
there  is  an  absolute  necessity  for  a  certain  amount  of  inert 
matter  to  distend  the  walls  of  the  alimentary  canal  and 
distribute  the  nutrient  material  so  that  it  may  the  more 
readily  be  absorbed. 

Too  large  an  amount  of  indigestible  material  in  the  food 
is,  on  the  other  hand,  not  satisfactory,  for  not  only  does  it 
require  of  the  different  organs  an  undue  amount  of  work  in 
handling  it,  but  the  indigestible  material  may  act  as  a 
positive  irritant  in  the  stomach  and  bowels.  Too  coarsely 
ground  cereals  sometimes  overstimulate  and  irritate  the 
mucous  surfaces  and  thus  become  a  source  of  impaired 
digestion. 

Not  only  should  the  food  contain  the  nourishing  material, 
but  this  should  be  of  such  a  character  that  it  is  just  adapted 
to  the  wants  of  the  body. 

In  order  to  find  out  what  the  human  body  needs  for  its 
sustenance  we  may  notice  either  the  composition  of  the 
body,  or  we  may  study  milk,  which  is  the  food  provided  by 
nature  to  nourish  the  young.  The  body  contains  the 
following  chemical  elements  :  oxygen,  carbon,  hydrogen, 
nitrogen,  phosphorus,  sulfur,  chlorin,  fluorin,  silicon,  cal- 
cium, potassium,  sodium,  magnesium,  iron,  manganese,  and 
copper  —  sixteen  in  all. 

The  fact  that  these  elements  are  found,  however,  means 
very  little,  if  we  have  no  information  as  to  how  they  are 
combined,  what  proximate  substances  or  compounds  they 
form,  for  these  elements  might  be  combined  to  form  innu- 
merable substances. 

According  to  a  recent  authority,1  the  body  of  a  man 
weighing  154  pounds  is  made  up  of  the  following  com- 
pounds, in  approximately  the  quantities  noted:  — 

i  A.  H.  Church,  "  Food,"  p.  6. 


USB   OF   FOODS 


123 


POUNDS 


OUNCES 


Water,  found  in  all  the  tissues        

Albumen,  myosin,  etc.,  found  in  muscular  flesh, 

chyle,  lymph,  and  blood 

Calcium  phosphate,  found  in  tissues  and  liquids, 

but  chiefly  in  the  bones  and  teeth  .... 
Fat,  distributed  through  the  body  .... 
Ossein,  or  collagen,  found  in  the  bones  and 

connective  tissues 

Creatin,  etc.,  in  the  skin,  nails,  and  hair  .  . 
Cartilagan,  found  in  the  cartilages  .... 
Haemoglobin,  a  substance  containing  iron,  found 

in  the  blood 

Calcium  carbonate,  in  the  bones 

Neurin  with  lecithin,  cerebrin,  and  similar  com- 
pounds, found  in  the  brain,  nerves,  etc.   .    . 
Calcium  fluorid,  found  in  the  bones  and  teeth 
Magnesium  phosphate,  chiefly  in  bones  and  teeth 
Sodium  chlorid,  throughout  the  body      .     .     . 
Cholesterin,   inosite,  and  glycogen,   which  are 

found  in  brain,  muscle,  and  liver  .... 
Sodium  sulfate,  phosphate,  carbonate,  &c.,  found 

in  all  liquids  and  tissues 

Potassium    sulfate,    phosphate,    and    chlorid, 

found  in  all  liquids  and  tissues 

Silica,  found  in  hair,  skin,  and  bone        .     .     . 


109 
16 

8 
4 

4 
4 
1 

1 
1 

0 
0 
0 
0 

0 
0 

0 
0 


0 
8.0 

12.0 
8.0 

7.8 
2.0 
8.0 

8.0 
0.8 

13.0 
7.4 
7.0 
7.0 

3.0 
2.2 

1.7 
0.1 


Besides  the  above  there  are  other  complex  compounds 
which  occur  in  small  quantities,  but  which  are  none  the 
less  of  importance.  Each  of  the  proximate  principles  is 
made  up  of  two,  three,  four,  or  possibly  more,  elements,  and 
the  compounds  thus  formed  are  some  of  them  very  com- 
plex in  their  structure. 

No  classification  of  food  is  very  satisfactory,  for  although 
we  may  adopt  the  classification  of  Liebig  and  divide  the 


124  SANITARY   AND   APPLIED   CHEMISTRY 

foods  into  the  carbonaceous,  or  those  which  furnish  heat, 
and  nitrogenous,  or  those  whose  function  it  is  to  build  up  the 
body  and  furnish  muscular  energy,  we  are  met  at  the  outset 
by  the  fact  that  a  large  number  of  foods  partially  fulfill 
both  functions.  The  cells  of  the  body  may  draw  their  sup- 
ply of  energy  from  proteids,  albuminoids,  carbohydrates,  or 
fats ;  but  material  for  the  manufacture  and  repair  of  tissues 
must  come  from  the  proteids.  Heat  is  produced  as  a  result 
of  cell  action.1 

The  proximate  substances  that  go  to  make  up  foods 
include  (1)  water,  (2)  fat,  (3)  carbohydrates,  (4)  protein  and 
related  nitrogenous  bodies,  (5)  organic  acids,  and  (6)  the 
mineral  salts.  Water,  although  absolutely  essential  as  a  con- 
stituent of  the  food  material,  need  not  be  considered  in  the 
light  of  a  nutrient.  The  fats  which  occur  both  in  vegetable 
and  animal  foods  are  glycerids  of  the  fatty  and  other  acids. 
They  contain  only  carbon,  oxygen,  and  hydrogen.  The 
oxygen  is  not  present  in  sufficient  quantity  so  that  with  the 
hydrogen  it  would  form  water.  Fats  are  more  fully  dis- 
cussed under  Soap,  p.  96,  also  on  p.  49  and  in  Chapter  XVIII. 

CARBOHYDRATE    FOODS 

The  carbohydrates  include,  with  a  few  exceptions,  only 
those  compounds  of  carbon,  hydrogen,  and  oxygen  in  which 
the  hydrogen  and  oxygen  are  in  the  proportion  to  form  water ; 
that  is,  two  parts  of  hydrogen  to  one  of  oxygen.  This  group 
includes  such  common  foods  as  starch  (C6H1005)n  and  cane 
sugar  (CtfH.gjOn).  These  foods  may  be  divided  into:  — 

1.  The  cellulose   group    (QJlJd^u   including  cellulose, 
starch,  inulin,  dextrins,  gum,  etc. 

2.  The  cane-sugar  group  (C^H^On),  including  cane  sugar, 
milk  sugar,  maltose,  etc. 

1  Hutchison,  "Food  and  Dietetics,"  p.  3. 


USE  OF   FOODS  125 

3.  The  glucose  group  (CgH^Og),  including  dextrose,  levu- 
lose,  grape  sugar,  starch  sugar,  and  galactose. 

In  addition  to  the  above,  inosite,  C6H1206,H20,  which  oc- 
curs in  muscular  tissues,  and  pectose,  the  jelly-producing 
substance  of  vegetables,  should  according  to  some  authors 
be  classified  as  carbohydrates. 

The  ordinary  analysis  of  a  food  stuff  includes  a  determina- 
tion of  the  amount  of  water,  fat,  nitrogenous  matter,  carbo- 
hydrates, and  ash.  A  study  of  these  analyses  is  of  value 
in  the  comparison  of  different  foods. 


CHAPTER  XI 
CELLULOSE,  STARCH,  DEXTRIN,  ETC. 

CELLULOSE  (C6H1005)n  is  the  main  product  of  vegetable  life, 
and  forms  the  principal  part  of  wood,  cotton,  filter  paper, 
etc.  In  fact,  cotton  fiber,  linen  rags,  and  "  washed  "  filter 
paper  are  nearly  pure  cellulose.  It  is  insoluble  in  most 
chemical  reagents,  but  may  be  dissolved  in  cuprammonia, 
and  from  the  solution  the  cellulose  may  be  precipitated  as 
a  gelatinous  mass  which  is  similar  to  aluminum  hydroxid 
in  appearance  and  dries  to  a  hard  mass. 

When  cotton  or  paper  is  treated  with  a  mixture  of  nitric 
and  sulfuric  acids,  a  substance  called  nitrocellulose  is 
formed.  One  variety  of  this  substance  is  gun  cotton.  When 
the  nitrocellulose  is  dissolved  in  ether  it  yields  collodion. 
Another  product  known  as  celluloid  is  made  by  dissolving 
certain  varieties  of  nitrocellulose  in  ether  and  camphor,  and 
afterwards  evaporating  off  the  solvent.  There  are  some 
special  properties  of  cellulose,  which  are  illustrated  in  the 
experiments  which  follow  this  section. 

Although  some  of  the  lower  animals,  as  the  rodents,  can 
digest  cellulose  and  make  it  available  for  nutrition,  the 
stomach  of  man  has  this  power  only  to  a  limited  extent. 
According  to  Atwater  some  of  the  cellulose  of  the  food  is 
absorbed,  but  much  of  it  passes  through  the  system  un- 
changed and  is  of  value  only  as  it  helps  distend  the  alimen- 
tary canal.  Whatever  digestion  takes  place  in  the  intestines 
is  due  to  the  action  of  certain  microorganisms,  by  which  fatty 
acids  are  produced,  which  upon  absorption  yield  nutriment. 

126 


CELLULOSE,   STABCH,   DEXTRIN,   ETC.  127 

Herbivorous  animals  eat  food  that  contains  large  amounts 
of  cellulose  associated  with  smaller  quantities  of  starch,  fat, 
and  nitrogenous  substances. 

Experiment  64.  To  3  volumes  of  water  add  1  volume  con- 
centrated sulfuric  acid  and  cool  the  mixture.  Pour  this  into 
an  evaporating  dish,  and  immerse  in  it  strips  of  unsized 
paper,  and  allow  to  soak  for  about  15  seconds.  Wash  thor- 
oughly, first  with  water,  then  with  dilute  ammonia  solution, 
and  again  with  water.  Dry  the  parchment  paper  or  amyloid 
thus  obtained,  and  notice  its  peculiar  properties.  Although 
it  has  undergone  a  physical  change,  it  still  has  the  composi- 
tion of  paper.  Unsized  cloth  may  be  treated  in  the  same 
way. 

Experiment  65.  Another  sample  of  unsized  paper  is 
treated  with  strong  sulfuric  acid,  and  allowed  to  stand  for 
5  minutes.  It  dissolves  into  a  pulpy  mass,  which  is  then 
washed  thoroughly,  and  tested  with  tincture  of  iodin.  If 
a  purple  color  is  produced,  it  is  an  indication  that  the 
cellulose  has  been  changed  to  dextrin. 

Experiment  66.  To  show  the  action  of  alkalies  on  cellu- 
lose, treat  a  piece  of  cotton  cloth  for  20  minutes  with  a  solu- 
tion of  sodium  hydroxid  of  a  specific  gravity  of  1.25.  Wash 
and  dry,  and  notice  the  change  in  the  structure  of  the  fiber. 
This  is  practically  the  process  used  to  make  "  mercerized  " 
goods.  In  this  process  the  linear  contraction  is  about  25%, 
and  the  increase  of  strength  is  50%. 

Experiment  67.  Make  cuprammonia  (Schweitzer's  re- 
agent), Cu  (NH3)4  S04,  as  follows:  Add  to  a  cold  solution  of 
copper  sulfate,  Cu  SO^  a  cold  solution  of  sodium  hydroxid, 
filter,  wash,  and  dissolve  in  concentrated  ammonium  hy- 
droxid and  add  a  little  dilute  sulfuric  acid.  Schweitzer's 
reagent  should  be  freshly  prepared,  and  "should  be  capable 


128  SANITARY   AND   APPLIED   CHEMISTRY 

of  immediately  dissolving  cotton  or  fine  grades  of  filter 
paper.  It  may  be  used  to  dissolve  cellulose  from  pectose, 
in  working  with  the  microscope. 

Experiment  68.  Dissolve  cotton  or  filter  paper  in 
Schweitzer's  reagent,  and  add  to  the  solution  an  excess  of 
hydrochloric  acid.  This  will  precipitate  the  cellulose, 
which  may  be  washed  on  a  filter  so  that  its  properties  can 
be  examined. 

STARCH  (CaH1005)x 

The  starches  are  regarded  as  the  most  important  of  the 
foods  of  this  group;  indeed,  they  form  the  principal  part  of 
most  vegetable  foods.  Starch  is  stored  up  in  seeds,  roots, 
fruits,  and  vegetables,  and  is  adapted  for  food  purposes; 
and  so  it  is  utilized  by  man  and  the  lower  animals.  As  the 
bee  stores  honey  for  future  use,  so  the  plants  store  starch 
for  the  use  of  the  germinating  seed,  and  man  takes  advantage 
of  both  kingdoms  of  nature.  The  carbohydrates  circulate 
through  the  plant  in  the  form  of  sugar,  but  they  are  stored 
up  in  the  form  of  starch,  and  this  store  can  be  drawn  from 
by  the  plant  in  time  of  need. 

Sources  of  Starch.  —  The  most  important  source  of  starch 
is  the  cereals.  The  amount  of  starch  contained  in  some 
grains  is  as  follows :  — 

PER  CENT  PM  Cwrr 

Wheat  flour 76.6      Rice 79.4 

Graham  flour 71.8  Buckwheat  flour  ....     77.6 

Corn  meal 71.0      Barley 62.0 

Oatmeal 68.1       Sorghum  seed 64.6 

Rye  flour 78.7      Millet 60.0 

Various  roots,  tubers,  and  stems  are  also  sources  of  starch, 
as  follows : l  — 

1  For  complete  composition,  see  "  Foods,  "  by  A.  H.  Church. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC.  129 

PER  CENT  PEE  CENT 

Potato 18.0  Artichokes  (gum  and  inulin)  10. 2 

Yam 16.3  Sweet  cassava  (tapioca)    .    30.98 

Sweet  potato       ....  16.0  Arrowroot  ( Maranta  arundi- 

Carrots  (pectose)    ...  2.5            nacece) 22.93 

Parsnips 3.6  Onions  (pectose,  etc.)  .     .      4.8 

Turnips  (pectose)    ...  3.0  Radishes  (carbohydrates) .      4.6 

Beets  (pectose)  ....  2.4 

Some  less  familiar  sources  of  starch  are  the  Bitter  cassava 
(tapioca),  Salep  (orchids),  Tous  les  mois  (Canna  edulis),  the 
sago  palm,  and  celery  roots. 

The  leguminous  plants  also  furnish  starch,  thus :  — 

PER  CENT  PER  CENT 

Beans 67.4      Peanuts 11.7 

Peas 51.0       Soy  beans 12.5 

Lentils 56.1 

There  is  some  starch  in  all  fruits,  but  those  mentioned 
are  of  special  value  on  account  of  the  amount  which  they 
contain:  — 

PEB  CENT  PER  CENT 

Bananas 22.0      Breadfruit 14.0 

Plantain 15  to  20 

Some  nuts  contain  considerable  starch,  thus :  — 

PER  CENT  PER  CENT 

Acorns 43.35       Horse  chestnuts   .     .     .     .68.25 

Chestnuts 42.1 

Of  the  above,  the  most  important  commercial  sources  of 
starch  are  wheat,  corn,  rice,  potatoes,  acorns,  and  chestnuts. 
A  special  variety  of  starch  is  also  put  on  the  market 
under  the  name  of  tapioca,  arrowroot,  and  sago.  The 
other  starch-bearing  vegetable  products,  as  well  as  those 
specially  noted,  are  used  in  some  countries  as  food. 

TVHBAT 

The  examination  of  the  wheat  grains  by  the  microscope 
shows  that  upon  the  outside  there  are  bran  cells ;  next  to 


130  SANITARY   AND   APPLIED   CHEMISTRY 

these  are  cells  of  a  thin  cuticle ;  within  these  are  the  gluten 
cells,  and  finally,  nearer  the  center  of  the  grain,  are  the  starch 
cells.  If  a  longitudinal  section  be  made  of  a  wheat  grain, 
and  it  is  examined  by  a  microscope  of  low  power,  it  will 
be  found  to  be  made  up  of  the  "  germ,"  which  is  near  one 
end,  the  "kernel,"  and  the "  bran,"  or  outer  envelope.1 

Wheat  is  a  typical  bread-making  cereal.  Its  proteids 
differ  from  those  of  other  cereals,  and  are  composed  chiefly 
of  a  globulin,  an  albumin,  a  proteose,  and  the  two  bodies, 
gliadin  and  glutenin.2  The  two  latter  form  the  gluten,  and 
give  the  characteristic  properties  to  wheat  flour.  The  prod- 
ucts of  wheat  are  used  as  human  food  in  many  forms. 
There  are  nearly  a  hundred  different  grades  of  food  materials 
made  from  wheat  by  the  patent-roller  process  of  milling.3 

Wheat  sown  in  the  fall  is  called  winter  wheat,  and  that 
sown  in  the  spring  is  spring  wheat.  The  kernels  of  winter 
wheat  are  usually  larger  and  softer  than  the  spring  variety. 
Spring  wheat  usually  contains  more  gluten  than  winter 
wheat. 

In  comparing  the  milling  and  the  food  value  of  wheat,  it 
should  be  remembered  that  this  depends  largely  on  the 
amount  of  nitrogenous  matter  present.  A  high  percentage 
of  proteids  is  not  always  a  sure  indication  of  the  milling 
value  of  the  wheat.  It  is  the  gluten  content  of  the  flour  on 
which  the  bread-making  qualities  chiefly  depend.  The  per- 
centage of  dry  gluten  is  considered  the  safest  index  to  use  in 
the  comparison  of  different  samples  of  flour. 

A  comparison  of  the  analysis  of  different  samples  of 
wheat  is  of  interest : 4  — 

1  For  full  description,  see  Jago,  "The  Science  and  Art  of  Bread 
Making,"  p.  265. 

2  Osborn  and  Voorhees,  Am.  Chem.  Jour,  Vol.  XV,  p.  392. 
•Bui.  13,  Pt.  9,  U.  S.  Dept.  Agric.,  Div.  Chem. 

*  Wiley,  Bui.  45,  U.  S.  Dept.  Agric.,  Div.  Chem. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC. 


131 


MOISTURE 

ALBUMI- 
NOIDS 

ETHER 
EXT. 

3RUDE 
FlBEE 

ASH 

CARBO- 
HYDRATES 

Domestic    .... 

10.62 

12.23 

1.77 

2.36 

1.82 

71.18 

Foreign      .... 
World's  Fair,  1893  . 
Mean,  given  by  Jen- 
kins &  Winton 

11.47 
10.85 

12.08 
12.20 

1.78 
1.74 

2.28 
2.35 

1.73 
1.81 

70.66 
71.09 

Spring     .     .     . 
Winter    .    .    . 

10.40 
10.50 

12.50 
11.80 

2.20 
2.10 

1.80 
1.80 

1.90 
1.80 

21.20 
72.00 

Mean,     by      Konig 
Miscellaneous  . 

13.37 

12.51 

1.70 

2.56 

1.79 

68.01 

Spring  Wheat  . 

13.80 

19  KR 

14.95 

17  fiK 

1.56 

1  K« 



2.19 
i  ftft 

67.93 

fift  7  A. 

There  are,  however,  some  special  varieties  of  wheat, 
including  a  Russian  wheat,  that  contain  more  protein. 
Twenty-four  analyses  of  this  variety  show  an  average  of 
21.56%  of  nitrogenous  substances.1  The  ash  of  wheat 
contains  about  30  %  of  potash,  3  %  of  lime,  12  <f0  of  magne- 
sia, and  47  %  of  phosphoric  anhydrid,  besides  the  other 
constituents  that  are  usually  found  in  the  ash  of  plants. 
From  this  it  is  easy  to  understand  that  a  large  amount  of 
mineral  matter  is  taken  from  the  soil  by  a  crop  of  wheat. 

•WHEAT  FLOUR 

Wanklyn  states  that  wheat  flour  has  the  following  com- 
position :  — 

PER  CENT 
Starch,  &c 69.0 


PER  CENT 
Water  16.5 


Ash 


0.7 


Fat 1.2 

Gluten,  &c 12.0 

As  wheat  flour  was  formerly  made,  it  was  crushed  between 
millstones,  forming  a  rather  coarse  product ;  this  was  bolted, 
and  gave  fine  flour,  middlings,  and  bran. 

At  the  present  time,  by  the  roller  process,  in  which  the 

1  Blyth,  "  Foods,  Their  Composition  and  Analysis,"  p.  146. 


132 


SANITABY   AND   APPLIED   CHEMISTRY 


grain  is  crushed  and  sifted  repeatedly,  a  large  number  of 
grades  of  flour  may  be  produced. 

The  highest  grade  of  flour  produced  is  known  as  Patent 
flour,  while  the  lower  grades  are  often  known  as  Family, 
Bakers',  and  Bed  Dog  flour.  The  following  analyses  show 
the  percentage  of  the  different  products  produced  from  the 
grain,  and  the  grades  obtained  by  different  millers :  — 


MUTJTK8OTA1 

ARKANSAS  * 

67  82 

17.66 

60.36 

11.28 

Low  grade  flour    

6.77 
17.64 

2.32 
24.10 

Shorts       

3.79 

1.10 

Screenings,  waste,  &c.        

2  70 

448 

100.00 

100.00 

The  commercial  value  of  a  flour  depends  on  its  color, 
texture,  and  the  quantity  of  gluten  which  it  contains.  The 
character  of  this  gluten  also  differs  under  different  condi- 
tions of  climate  and  soil.  Bakers  prefer  a  flour  with  a  high 
percentage  of  tenacious  gluten,  which  permits  the  produc- 
tion of  a  loaf  of  bread  containing  a  maximum  amount  of 
water.  This  water  may  be  as  high  as  40  %.3  In  large 
bakeries  the  best  results  are  obtained  by  mixing  different 
grades  of  flour. 

ANALTSIS   OF  DIFFERENT   KINDS   OF  FLOUR 

Some  of  the  constituents  of  different  kinds  of  flour  are 
as  follows : 4  — 

1  Snyder,  Minn.  Agric.  Exp.  Sta.,  Bui.  90. 

2  Teller,  Ark.  Agric.  Exp.  Sta.,  Buls.  42,  63. 

1  U.  S.  Dept.  Agric.,  Div.  Chem.,  Bui.  13,  Pt.  9. 
4  Bui.  13,  Pt.  9,  U.  S.  Dept.  Agric.,  Bu.  Chem. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC. 


133 


Mown;  BE 

NITROGEN 
N  x  6.25 
PBOTEIDS 

DBT 
GLUTEN 

ETHER 
EXTRACT 

NITROGEN 
FREE 
EXTRACT 

Patent  wheat  flour 

12.77 

10.65 

9.99 

1.02 

74.76 

Common   market 

wheat  flour.  .    . 

12.28 

10.18* 

9.21 

1.30 

75.63 

Bakers'  and  family 
flour     .... 

11.69 

12.28 

13.07 

1.30 

73.87 

Indian-cornflour  . 

12.57 

7.13 



1.33 

78.36 

Eye  flour     .     .     . 
Barley  flour      .     . 
Buckwheat  flour  . 

11.41 
10.92 
11.89 

13.56 
7.50 
8.75 



1.97 
.89 
1.58 

73.37 
80.60 
75.41 



For  a  comparison  of  the  different  grades  of  wheat  flour, 
the  following  table,  which  gives  the  results  of  work  done  at 
the  University  of  Minnesota,1  is  of  interest :  — 


MILLING  PRODUCT 

WATER 

PROTEIN 
NX  5.7 

FAT 

CARBO- 
HYDRATES 

ASH 

PHOSPHORIC 
ACID 

First  patent  flour 

10.55 

11.08 

1.15 

76.85 

0.37 

0.15  per  ct. 

Second  pat.  flour 

10.49 

11.14 

1.20 

76.75 

.42 

.17 

Straight  or 

Standard  patent 

10.54 

11.99 

1.61 

75.36 

.50 

.20 

First  clear- 

grade  flour  .     . 

10.13 

13.74 

2.20 

73.13 

.80 

.34 

Second  clear- 

grade  flour  .     . 

10.08 

15.03 

3.77 

69.37 

1.76 

.56 

"Bed  Dog  "flour 

9.17 

18.98 

7.00 

61.37 

3.48 



Shorts  .... 

8.73 

14.87 

6.37 

65.47 

4.56 



Bran    .... 

9.99 

14.02 

4.39 

65.54 

6.06 

2.20 

Entire-wheat 

flour  .... 

10.81 

12.26 

2.24 

73.67 

1.02 

.54 

Graham  flour     . 

8.61 

12.65 

2.44 

74.68 

1.72 

.71 

Wheat  ground 

in  laboratory    . 

8.50 

12.65 

2.36 

74.69 

1.80 

.75 

Gluten  flour  .     . 

8.57 

16.36 

3.15 

70.63 

1.29 



1  Synder,  U.  S.  Dept.  Agric.,  O.  Exp.  Sta.,  Bui.  101. 


134  SANITARY   AND   APPLIED   CHEMISTRY 

From  the  figures  in  the  table  it  will  be  seen  that  there  is 
a  gradual  decrease  in  the  water  content  from  the  first  patent 
to  the  "  red  dog "  grade  of  flour,  and  there  is  a  noticeable 
increase  in  the  ash  from  the  higher  to  the  lower  grades. 
The  determination  of  ash  has  been  taken  advantage  of  to 
determine  the  grade  of  a  particular  sample  of  flour. 

There  is  but  little  difference  in  chemical  composition  be- 
tween the  first  and  second  grades  of  patent  flour.  The 
"  standard  "  patent  flour  contains  about  12  per  cent  of  pro- 
tein, while  the  wheat  from  which  it  was  made  contains 
12.65%.  The  second  clear  and  "red  dog"  samples  are 
characterized  by  a  high  per  cent  of  protein,  fat,  and  ash. 
Judging  by  their  proximate  composition  only,  these  latter 
flours  might  appear  to  have  a  higher  nutritive  value  than 
the  higher  grades ;  but  when  judged  by  the  character  of  the 
bread  made  from  them,  they  must  be  assigned  a  much  lower 
value  (see  p.  175). 

The  wheat  product  of  the  United  States  for  1905  was 
692,979,489  bu.1 

CORN   (MAIZE) 

Corn,  though  coming  originally  from  America,  has  been 
largely  cultivated  in  some  other  countries.  It  grows  well 
in  temperate  and  warm  climates  all  over  the  world.  The 
grains  keep  well,  and  may  be  parched,  or  ground  into  meal. 
There  are  a  large  number  of  varieties  of  corn,  a  special 
variety  being  adapted  to  each  special  climate. 

Some  of  the  preparations  of  corn  are  hominy,  samp,  corn 
meal,  cracked  corn,  cerealin,  and  a  large  number  of  corn 
starches.  The  examination  of  the  analyses  made  by  the 
Department  of  Agriculture 2  shows  that  corn  has  the  follow- 
ing composition :  — 

PER  CENT  PEE  CENT 

Moisture 10.04       Crude  fiber 2.09 

Albuminoids 10.39       Ash 1.56 

Ether  extract  (mostly  fats)      5.20  Carbohydrates    ....     70.69 

1  Ann.  Kep.  1  Jept.  Agric.          2  Bui.  45,  Dept.  Agric. ,  Div.  Chem. ,  p.  25. 


CELLULOSE,   STAJRCH,   DEXTRIN,   ETC.  135 

Corn  is  especially  rich  in  fats,  although,  somewhat  deficient 
in  nitrogenous  matters  and  mineral  salts.  It  is  a  very  fat- 
tening food,  both  for  man  and  the  lower  animals.  As  it 
was  first  introduced  into  Europe  as  food  for  lower  animals, 
it  has  been  somewhat  difficult  to  overcome  the  prejudice 
of  the  people  against  it,  although  the  United  States  gov- 
ernment has  sent  a  commission  to  Europe  to  demonstrate 
to  the  people  the  value  of  corn  as  a  food.  Corn  meal  is 
quite  digestible,  though  slightly  laxative.  Cornstarch  is 
frequently  used  as  a  substitute  for  other  starches  in  food 
for  invalids.  In  this  country,  both  yellow  corn  meal, 
made  from  hard  corn  of  the  Northern  States,  and  white 
corn  meal,  made  from  the  white  corn  of  the  West,  are  in  use. 

Referring  to  the  relative  nutritive  properties  of  wheat  and 
maize,  Wiley *  says :  "There  is  a  widespread  opinion  that  the 
products  of  Indian  corn  are  less  digestible  and  less  nutritious 
than  those  from  wheat.  This  opinion,  it  appears,  has  no 
justification,  either  from  the  chemical  composition  of  the 
two  bodies,  or  from  recorded  digestive  or  nutritive  experi- 
ments. In  round  numbers,  corn  contains  twice  as  much  fat 
or  oil  as  wheat,  three  times  as  much  as  rye,  twice  as  much 
as  barley,  and  two  thirds  as  much  as  hulled  oats.  Indian 
corn  has  nearly  the  same  content  of  nitrogenous  matters  as 
the  other  cereals,  with  the  exception  of  oats." 

The  corn  crop  of  the  United  States  amounted  to  2,707,- 

993,540  bu.2  in  1905. 

OATS 

Oats  are  grown  in  northern  regions  throughout  the  civilized 
world.  The  composition  of  oatmeal  is  as  follows : 3  — 

PER  CENT  PER  CENT 

Water 12.92  Dextrin  and  Gum    ...      2.04 

Nitrogenous  matter      .     .     11.73       Starch 51.17 

Fats 6.04       Fiber 10.83 

Sugar 2.22       Ash 3.05 

1  U.  S.  Dept.  Agric.,  Div.  Chem.,  Bui.  13,  Pt.  9,  p.  1290. 

2  Ann.  Rep.  Dept.  Agric. 

•  Blyth,  "Foods,  Their  Composition  and  Analysis,"  p.  170. 


136  SANITARY   AND   APPLIED   CHEMISTRY 

Oatmeal  contains  considerable  fat,  protein,  and  mineral 
salts.  The  nitrogenous  substance  is  composed  of  "  gliadin  " 
and  plant  casein.  The  gliadin  has  a  much  higher  percent- 
age of  sulfur  than  the  gliadin  of  wheat.  Von  Bibra  states 
that  oatmeal  contains  from  1.24  to  1.52%  of  albumen.  It 
has  proved  an  excellent  food  stuff,  though,  on  account  of  the 
quality  of  the  gluten,  it  is  not  adapted  to  use  for  making 
bread.  Within  the  last  forty  years  it  has  come  into  extensive 
use  in  the  United  States  as  a  breakfast  food.  It  is  stated 
that  the  so-called  Scotch  groats  are  prepared  by  removing 
the  outer  husks  and  leaving  the  grain  almost  whole,  and 
then  this  is  ground  between  millstones.  True  Scotch  groats 
are  heated  over  perforated  iron  plates  and  slightly  parched 
before  being  ground.  In  most  cases  where  oatmeal  can  be 
digested,  it  forms  a  very  valuable  food,  but  it  requires  long 
cooking  and  considerable  skill  in  preparation  to  make  it 
wholesome.  On  this  account,  although  it  has  been  used  so 
extensively  for  many  years,  recently  other  foods  have  to 
some  extent  been  substituted  for  it.  Possibly  we  have  not 
appreciated  the  fact  that  it  is  a  very  hearty  food  and  es- 
pecially suitable  for  those  who  live  an  outdoor  life.  The 
oat  crop  of  the  United  States  for  1905  was  953,216,197  bu.1 

RYE 

This  cereal  grows  best  in  northern  countries,  where  it  is 
sown  in  the  fall  and  protected  by  the  covering  of  snow 
in  the  winter.  It  is  the  favorite  food  of  northern  Europe, 
where  it  is  made  into  "black  bread."  It  was  formerly 
quite  extensively  used  as  food  in  the  extreme  northern  part 
of  the  United  States.  The  grain  is  also  much  used  for 
malting  purposes.  It  makes  a  better  bread  when  mixed 
with  wheat  flour  in  the  proportion  of  two  of  wheat  to  one  of 
rye.  This  grain  is  more  liable  than  other  cereals  to  be 
affected  by  the  fungus  known  as  ergot.  Grain  that  is  modi- 
1  Ann.  Rep.  Dept.  Agric. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC.  137 

fied  in  this  way  is  unwholesome  and  may  be  poisonous.  On 
account  of  its  composition  rye  dough  is  very  sticky,  and  of 
a  dark  color.  The  composition  of  American  rye  is  as 
follows : 1  — 

MOISTURB     ALBUMINOIDS     ETHER  EXTRACT     CRUDE  FIBER     Asa     CARBOHYDRATE 
8.6  11.32  1.94  1.46          2.09  74.52 

The  rye  crop  of  the  United  States  for  1905  was  28,485,952 2 
bushels. 

BARLEY 

This  grain  was  originally  a  native  of  western  Asia,  and  is 
well  adapted  to  high  northern  latitudes.  Both  barley  meal 
and  "  pearl  barley, "  that  is,  the  grain  deprived  of  the  outer 
coating  by  attrition,  are  used  as  food.  By  far  the  largest  part 
of  the  barley  that  is  grown  is  used  for  making  malt  (see 
Chapter  XXIII).  Barley  flour  does  not  yield  a  light  bread, 
but  may  be  mixed  with  wheat  flour  for  this  purpose.  The 
following  is  the  composition  of  the  grain : 1  — 

MOISTURE     ALBUMINOIDS     ETHER  EXTRACT     CRUDE  FIBER     ASH     CARBOHYDRATE 
11.31  10.61  2.09  4.07  2.44         69.47 

136,651,020 2  bushels  of  barley  were  produced  in  the  United 
States  in  1905. 

RICE 

This  cereal  is  a  native  of  India  and  is  grown  in  the  East, 
in  southern  Europe,  and  in  the  southern  United  States, 
where  it  was  introduced  in  1644.  For  its  successful  culti- 
vation an  abundance  of  water,  so  that  the  fields  can  be  irri- 
gated, and  a  high  temperature  are  required.  Although  rice 
is  deficient  in  albuminoids,  fat,  and  mineral  matter,  yet  it  is 
estimated  that  it  is  the  main  food  of  a  third  of  the  human 
race.3  To  prepare  the  grain  for  the  market  it  is  separated 
from  the  hulls,  in  a  mill  of  special  construction,  and  for  the 

1  Bui.  45,  U.  S.  Dept.  Agric.,  Div.  Chem. 

a  Ann.  Rep.  Dept.  Agric.  8  A.  H.  Church,  "  Food,"  p.  88. 


138 


SANITARY   AND   APPLIED   CHEMISTKY 


European  market  it  is  glazed  by  shaking  in  a  drum  lined 
with  sheepskin.  The  grains  are  also  ground  into  flour  or 
may  be  used  for  making  starch.  Rice  has  the  following 
composition,  according  to  Konig : 1  — 


MOISTURE 

ALBUMIN- 
OIDS 

ETHER 
EXTRACT 

CRUDE 
FIBER 

ASH 

CARBO- 
HYDRATES 

Hulled 

12.58 

6.73 

1.88 

1.63 

0.82 

76.46 

Polished 

12.62 

7.52 

.84 

.48 

.64 

78.00 

This  grain  is  exceedingly  digestible  when  cooked,  especially 
by  steaming,  so  that  the  individual  grains  are  softened  and 
swollen.  It  cannot  be  made  into  bread  unless  mixed  with 
wheat  or  rye  flour,  as  it  is  deficient  in  gluten. 

It  is  evident  from  the  composition  of  rice  that  it  is  not 
fit  to  use  as  an  exclusive  food,  but  should  be  eaten  with 
butter,  eggs,  and  milk,  as  in  puddings,  or  with  meat,  fish,  peas, 
or  beans,  to  supply  the  necessary  food  ingredients.  When 
rice  is  cooked  in  a  soup  or  with  meat,  the  mineral  salts,  which 
at  best  are  not  very  abundant,  are  not  dissolved  in  water 
which  is  thrown  away,  but  are  fully  utilized  in  the  food. 
The  rice  production  in  the  United  States  in  1905  was 

377,971,917  lb.2 

POTATOES 

The  potato,  Solanum  tuberosum,  is  closely  allied  botani- 
cally  to  several  interesting  plants,  including  the  tomato, 
tobacco,  henbane,  and  capsicum.  Although  a  native  of  Chili 
and  Peru,  it  was  probably  carried  to  Spain  early  in  the  six- 
teenth century,  and  introduced  into  Virginia  from  Florida 
by  the  Spanish  explorers,  and  into  Great  Britain  from  Vir- 
ginia in  1565  by  Sir  John  Hawkins.8  The  potato  was 
recommended  by  the  Royal  Society  of  London  in  1663  for 

1  Bui.  46,  U.  S.  Dept.  Agric.,  Div.  Chem.,  p.  34. 

*  Ann.  Rep.  Dept  Agric.        8  Prof.  L.  H.  Bailey,  Universal  Cyclopedia. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC.  139 

introduction  into  Ireland  as  a  safeguard  against  famine.  It 
is  a  question  whether  its  introduction  there  has  not  aggra- 
vated the  famine  tendency,  since  the  peasants  learned  to 
depend  almost  entirely  on  potatoes,  and  from  disease  this 
crop  sometimes  failed.  It  was  not  cultivated  in  New  Eng- 
land till  the  eighteenth  century,  when  it  was  introduced  from 
Ireland ;  and  now  this  "  much  traveled  "  tuber  is  one  of  the 
most  important  articles  of  food. 

Potatoes  grow  well  and  are  a  staple  crop  in  the  New 
England  States,  New  York,  Michigan,  Canada,  and  through- 
out the  Middle  West.  Even  where  the  season  from  frost  to 
frost  is  quite  short  a  good  crop  may  be  raised.  260,741,204 1 
bu.  were  grown  in  the  United  States  in  1905. 

The  following  analysis  is  given  by  Church : 2  — 

PER  CENT  PEE  CERT 

Water 76.0  Dextrin  and  pectose     .    .    2.0 

Albuminoids 1.2    Fat 3 

Extractives,  as  solanin  and 

organic  acids       ....      1.5    Cellulose 1.0 

Starch 18.0  Mineral  matter     ....    1.0 

This  shows  that  93%  of  the  potato  is  water  and  starch, 
and  that,  as  in  the  case  of  rice,  the  amount  of  fat,  albumi- 
noid, and  mineral  matter  is  very  small.  But  with  even 
this  small  amount  of  nitrogenous  substance,  experiments 
have  proved  that  only  49%  of  this  is  proteids,  the  remain- 
der being  ammonium  compounds  and  salts,  which  are  of  no 
value  as  nutrients.  The  grains  of  potato  starch  are  very 
large  as  compared  with  those  of  the.  cereals.  Commercial 
starch  is  readily  obtained  from  this  tuber  and  this  is  a 
convenient  method  for  utilizing  small  and  immature  po- 
tatoes. The  starch  is  also  very  readily  attacked  by  ferments, 
and  so  potatoes  are  often  used  as  an  ingredient  of  home- 
made yeast. 

A  cross  section  of  the  potato  shows  that  it  is  made  up  of 
i  Ann.  Kep.  Dept.  Agric.  2  A.  H.  Church,  "  Food,"  p.  102. 


140  SANITARY   AND   APPLIED   CHEMISTRY 

a  rind,  which  constitutes  2^% ;  a  fibrovascular  layer, 
and  the  flesh,  89  % ;  and  an  analysis l  has  shown  that  the 
fibrovascular  layer  is  much  richer  in  mineral  matter  and 
proteids  than  the  body  of  the  potato,  so  by  the  ordinary 
method  of  peeling,  much  valuable  nutrient  material  is 
lost.  It  is  estimated  that  20%  of  the  actual  weight  of 
the  potato  is  usually  thrown  away  as  refuse.  The  mineral 
matter  is  rich  in  potash  salts,  and  when  the  potato  is  peeled 
before  boiling,  much  of  this  and  of  the  valuable  proteid 
matter  is  dissolved  and  wasted.  If  potatoes  must  be  peeled, 
there  is  less  loss  of  nutrient  material  if  they  are  plunged 
immediately  into  boiling  water  and  boiled  rapidly.  Potatoes 
may  also  be  steamed  or  baked  without  appreciable  loss. 

Potatoes  are  evidently  not  suited  for  use  as  the  staple 
article  of  diet,  but  are  extremely  useful  as  food  when  eaten 
with  butter,  milk,  meat,  eggs,  and  fish,  and  this  is  indeed 
the  ordinary  method  of  using  them.  They  are  very  valua- 
ble to  prevent  scurvy,  and  usually  form  a  staple  article  of 
food  upon  shipboard,  where  salt  meats  are  necessarily  used. 

SWEET   POTATOES 

The  sweet  potato  belongs  to  the  convolvulus  family,  and 
is  probably  a  native  of  tropical  America,  though  it  grows 
well  in  temperate  climates.  The  yam  is  a  different  plant, 
although  there  is  a  resemblance  between  the  tubers  of  this 
plant  and  the  sweet  potato.  Sweet  potatoes  have  the 
following  composition  : 2  — 

PER  CKNT  PIE  Curt 

Water 76.0  Pectose 9 

Albuminoids,  etc.     ...      1.5  Fat 4 

Starch 15.0  Cellulose 1.8 

Sugar 1.7  Mineral  matter     ....     1.6 

Dextrin  and  gum     .     .     .       2.2 

1  Bui.  43,  U.  S.  Dept.  of  Agric.,  Office  of  Exp.  Sta.,  1897,  p.  30. 

2  Church,  "  Food,  "  p.  107. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC.  141 

CASSAVA  (TAPIOCA) 

Tapioca  is  a  starch  product  made  from  the  roots  of 
several  plants  of  the  manioc  family,  that  grow  in  parts 
of  South  America  and  in  other  tropical  regions.  One  of 
these,  the  Manihot'-utilissima,  or  bitter  cassava,  yields  a 
milky  juice,  which  in  the  preparation  of  the  tapioca  is 
mixed  with  the  starch,  and  this  contains  considerable  of  the 
poison  known  as  prussic  acid,  HCN.  In  the  preparation 
of  the  tapioca,  this  juice  is  washed  away  from  the  grated 
root  and  the  pulp  is  heated  on  hot  plates,  to  drive  off  the 
last  of  the  prussic  acid ;  this  treatment  also  ruptures  most 
of  the  starch  grains.1  Tapioca  is  considered  one  of  the  most 
useful  foods  for  invalids.  A  tapioca  flour  is  also  made  by 
grinding  the  dried  pulp,  and  this  forms  the  chief  food  of 
the  natives  in  many  tropical  countries.  "  Pearl  tapioca  "  is 
often  made  from  potato  starch. 

ARROWROOT 

The  commercial  arrowroot  is  made  from  the  rhizome  of 
the  Maranta  arundinacea,  a  plant  growing  in  the  West 
Indies.  The  roots  are  washed,  reduced  to  a  pulp  and 
mixed  with  water,  strained,  and  from  the  milky  water  the 
starch  settles  out.  The  granules  of  the  starch  thus  pre- 
pared are  among  the  largest  used  in  commerce.  The  prod- 
uct when  cooked  is  one  of  the  most  valuable  foods  for  the 
diet  of  invalids.  In  making  the  so-called  Bermuda  arrow- 
root, great  care  is  observed  to  keep  it  from  contamination. 

SAGO 

This  form  of  starch  is  made  from  the  pith  of  the  sago 
palm,  which  grows  in  Sumatra,  Java,  Borneo,  and  the  West 
Indies.  The  starch  is  washed  out  of  the  pith  after  the  tree 

44,  U.  S.  Dept.  Agric.,  Div.  Chem. 


142  SANITARY   AND  APPLIED   CHEMISTRY 

has  been  felled,  and  is  converted  into  "  pearl "  sago  by  granu- 
lation.    A  palm  tree  frequently  yields  500  Ib.  of  sago. 

OTHER   STARCHY   FOODS 

Chestnuts  contain  15%  of  sugar  and  from  25  to  40%  of 
starch.  Although  used  for  making  bread  by  the  French, 
Spanish,  and  Italians,  it  is  not  a  very  digestible  form  of 
starch. 

Some  of  the  other  starches  of  interest  are  salep,  which 
is  made  in  Smyrna,  from  a  species  of  orchid,  and  is  used 
in  Turkey  and  the  East  as  food ;  Tons  les  Mois,  manufac- 
tured in  the  West  Indies  from  the  tubers  of  Canna  edulis  ; 
and  a  starch  prepared  in  Japan  from  the  bulbs  of  several 
varieties  of  lily. 

All  the  more  expensive  starches  are  liable  to  adulteration 
with  cheap  starches,  such  as  that  of  wheat,  corn,  or  rice, 
and  these  adulterations  can  only  be  detected  by  the  use  of 
the  microscope. 

LEGUMES 

Under  the  general  name  of  pulse  may  be  classified  such 
important  foods  as  peas,  beans,  soy  beans,  lentils,  etc., 
which  come  from  the  leguminous  plants.  It  is  said  that 
peas  came  originally  from  the  country  around  the  Black 
Sea.  Beans  were  introduced  into  Europe  from  India,  and 
lentils  were  grown  from  the  earliest  times  in  southern 
Europe  and  the  country  to  the  east  and  south  of  the 
Mediterranean  Sea.  The  soy  bean  is  an  important  article 
of  food  in  China  and  Japan,  and  supplements  very  well  the 
rice  diet  in  these  countries. 

These  foods  are  characterized  by  containing  not  only 
large  quantities  of  starch,  but  proteids  as  well,  so  they 
may  be  considered  as  furnishing,  at  the  same  time,  both 
kinds  of  nourishment  needed  by  the  body.  On  this  account, 
the  legumes  are  often  classified  with  the  nitrogenous  foods. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC. 


143 


Plants  of  this  family  have  a  special  provision  for  getting 
enough  nitrogen  for  their  growth,  in  the  little  nodules  on 
the  roots,  which  consist  of  masses  inclosing  bacteria,  which 
have  the  power  of  fixing  the  free  nitrogen  of  the  air  so  it  can 
be  utilized  by  the  growing  plant.  Peas  and  beans  also 
contain  some  sulfur  and  phosphorus,  in  combination  with 
the  nitrogenous  body  known  as  legumin,  or  vegetable  casein. 

Legumin  of  the  unripe  peas  appears  to  be  more  soluble 
and  more  readily  digested  than  that  from  the  dried  seeds. 
On  the  whole,  the  leguminous. foods  are  not  readily  digested 
in  the  stomach,  but  are  quite  thoroughly  absorbed  in  the 
intestines.1  If,  however,  the  food  is  not  ground  to  a  state 
of  very  fine  subdivision,  there  is  quite  a  loss  of  proteids 
in  the  process  of  digestion. 

The  following  analyses  are  given  by  Hutchison:2 — 


CARBO- 

MINERAL 

WATEB 

PROTEIDS 

HYDRATES 

FAT 

CELLULOSE 

MATTER 

Green  peas  .    . 

78.1 

4.0 

16.0 

0.5 

0.5 

0.9 

Dried  peas  .    . 

13.0 

21.0 

65.4 

1.8 

6.0 

2.6 

Beans     .     .    . 

11.7 

28.0 

55.8 

2.3 

4.0 

3.2 

Lentils    .    .    . 

11.7 

23.2 

58.4 

2.0 

2.0 

2.7 

While  the  leguminous  foods  are  excellent  diet,  yet  they 
should  be  supplemented  by  the  food  containing  starch  and 
fat,  and  so  we  use  beans  and  rice,  or,  more  commonly,  baked 
beans  and  fat  pork.  In  the  latter  case,  the  oil  or  melted 
fat  permeates  the  mass  in  cooking,  and  flavors  the  beans, 
and,  at  the  same  time,  furnishes  a  more  digestible  diet  than 
if  the  same  amount  of  fat  was  used  for  frying. 

Experiment  69.  To  prepare  legumin,  powder  some  peas 
and  treat  the  flour  with  successive  quantities  of  cold  water, 
made  slightly  alkaline.  In  this  solution  precipitate  the 

1  Hutchison,  "  Food  and  Dietetics,"  p.  223.          2  Idem,  p.  225. 


144  SANITARY   AND   APPLIED   CHEMISTRY 

legumin  with  acetic  acid.  To  purify,  dissolve  the  pre- 
cipitate in  weak  potassium  hydroxid  solution  and  reprecipi- 
tate  with  acetic  acid.  The  pure  alkaline  solution  should 
give  a  violet  color,  with  copper  sulfate  solution.1 

Green  peas  and  green  beans,  as  well  as  "  string  beans,"  do 
not  furnish  a  very  highly  nutritive  diet,  as  they  contain 
from  80  to  90%  of  water,  but,  on  account  of  the  ready 
solubility  of  the  proteids  and  their  agreeable  flavor,  they 
form  a  valuable  food  product. 

On  account  of  the  cheapness  of  this  form  of  proteid 
food,  a  pea  sausage  (Erbswurst)  has  been  introduced  as  a 
part  of  the  rations  in  the  German  army.  It  is  a  cooked 
food,  made  of  pea  meal  mixed  with  fat  pork  and  salt,  so 
prepared  that  it  will  not  readily  spoil.2  In  cases  where 
it  is  necessary  to  economize  in  the  cost  of  food,  this  can  be 
readily  attained  by  the  use  of  relatively  large  quantities 
of  peas,  beans,  and  lentils,  for  they  contain  large  amounts 
of  nutrients  at  a  comparatively  low  cost. 

BANANAS 

The  banana,  although  a  variety  of  the  plantain  family,  is 
smaller  and  more  delicate  in  flavor  than  the  common  plan- 
tain. Although  the  banana  grows  as  far  north  as  Florida, 
yet  the  climate  best  adapted  to  its  cultivation  is  that  of 
Cuba,  Jamaica,  the  Congo  region  in  Africa,  and  especially 
Central  America. 

The  tree  grows  to  a  hight  of  from  12  to  40  feet.  When 
the  stalk  of  the  tree  is  cut  down,  new  stalks  shoot  up  from 
the  roots.  The  tree  is  propagated  on  a  new  plantation,  not 
by  seeds,  but  by  cutting  off  roots  from  old  plants,  and  plant- 
ing in  rows,  very  much  like  the  hills  of  corn.  The  banana 
comes  to  maturity  from  the  root  in  from  ten  to  twelve 

1  Blyth,  "  Foods,  Their  Composition  and  Analysis,"  p.  181. 
«  Thompson,  "  Practical  Dietetics,"  p.  163. 


CELLULOSE,   STARCH,    DEXTRIN,   ETC. 


145 


months.  Each  bunch  that  is  produced  will  contain  from 
150  to  180  bananas. 

The  banana-growing  industry  has  increased  enormously  in 
the  past  thirty  years,  and  at  the  same  time  the  cost  of  the 
fruit  has  decreased.  Bananas  which  a  few  years  ago  cost 
10  cents  apiece  can  now  be  bought  at  from  10  to  15  cents 
a  dozen.  The  fruit  is  shipped  to  the  United  States  in  fast 
steamers  that  are  capable  of  carrying  40,000  bunches  per 
trip.  In  1905,  33,000,000  bunches  were  shipped  into  the 
United  States,  or  an  estimated  consumption  of  forty  bananas 
per  year  per  capita. 

Bananas  are  peculiar  in  combining  the  sweet  qualities  of 
a  fruit  with  the  nourishing  qualities  of  a  vegetable.  On 
account  of  the  presence  of  so  much  nutriment,  and  because 
bananas  grow  so  luxuriantly,  it  is  stated  that  a  given  area 
of  ground  will  support  a  greater  population  if  planted  to 
bananas  than  if  planted  with  wheat. 

The  analysis  of  bananas  compared  with  some  other  starchy 
foods  is  as  follows  :  — 


RIPE 
BANANAS  1 

POTATOES  2 

BANANA  FLOUB 

FEOM 

RIPE  FRUIT* 

WHEAT 
FLOUB  s 

Moisture  .... 

73.10 

78.3 

13.0 

13.8 

Nitrogenous 
substances  .    . 
Fat      

1.87 
.63 

2.2 
.1 

4.0 
.5 

7.9 
1.4 

N.-free  extract     . 

23.05 

18.4 

Carbohydrates 
Cellulose     .    .    . 
Ash     

.29 
1.06 

1  0 

80.0 
2.5 

76.4 
.5 

From  this  analysis  it  is  evident  that  bananas  are  rich  in 
sugar  or  starch  and  contain  a  fair  quantity  of  proteids. 

1  Kb'nig,  "  Chem.  d.  M.  Nah.  u.  Genuss.,"  p.  1120. 

2  Rep.  Ct.  Agric.  Ex.  Sta.        8  Hutchison,  p.  249. 


146  SANITARY   AND   APPLIED   CHEMISTRY 

Some  persons  find  bananas  difficult  of  digestion,  but  this 
is  no  doubt  due  to  the  fact  that  they  are  often  picked  so 
green  that  they  are  irregularly  ripened.  The  imperfectly 
ripened  fruit  is  composed  chiefly  of  starch,  and  this  should 
be  cooked  before  it  is  eaten,  especially  by  invalids.  As  the 
fruit  ripens  naturally,  however,  this  starch  changes  to  a  mu- 
cilaginous substance,  and  then  to  dextrin  and  glucose. 

A  banana  flour  is  made  by  carefully  drying  selected  and 
fully  ripened  bananas.  It  is  said  to  be  easily  digested  and 
extremely  nutritious.  This  is  about  the  only  fruit  flour  that 
can  be  readily  made,  and  so  it  has  been  used  with  success  as 
a  part  of  the  diet  of  patients  suffering  from  gastric  irrita- 
bility and  similar  diseases.  A  plantain  meal  is  made  by 
drying  the  inside  of  the  unripe  fruit. 

GENERAL  METHOD    FOR    MAKING   STARCH 

In  the  United  States  starch  is  made  especially  from  corn 
(maize),  wheat,  and  potatoes ;  in  Europe,  potatoes,  corn,  and 
rice  are  used  ;  and  in  the  West  Indies  starch  is  made  espe- 
cially from  arrowroot  or  the  sago  palm. 

Several  processes  are  used  for  the  manufacture  of  starch. 
In  making  cornstarch  by  the  Durgen  system  a  continuous 
stream  of  water  at  140°  F.  is  allowed  to  flow  over  the  corn 
for  three  days  in  order  to  soften  it.  It  is  then  ground  in 
water,  and  the  milky  liquid  is  run  into  nearly  horizontal 
revolving  sieves,  or  square  shaking  sieves.  The  starch 
passes  through  the  bolting  cloth,  and  the  refuse,  which  con- 
sists of  the  cellular  tissue,  is  retained.  The  refuse  is  after- 
wards pressed  and  used  for  cattle  food.  The  water,  holding 
the  starch  in  suspension,  is  allowed  to  stand  in  wooden  vats 
until  the  starch  settles  out,  when  it  is  finally  drawn  off. 
In  order  to  purify  the  starch  and  remove  the  gluten,  the 
crude  starch  is  agitated  with  a  solution  of  caustic  soda, 
allowed  to  settle,  and  the  clear  liquid  drawn  off.  Next 


CELLULOSE,   STARCH,   DEXTRIN,   ETC.  147 

the  starch  is  washed  and  run  into  a  deep  vat,  and  the  high- 
est of  a  series  of  plugs  is  removed  from  the  side  to  allow 
the  starchy  liquid  to  run  out.  A  little  later  a  lower  plug  is 
removed,  and  so  on  until. the  vat  is  nearly  empty;  then  a 
fresh  lot  of  starch  water  is  run  in.  The  products  from 
the  different  lots  of  starchy  water  drawn  off  are  of  different 
grades  and  used  for  different  purposes.  After  again  sifting 
through  bolting  cloth,  the  starch  solution  is  run  into  wooden 
settling  boxes,  and  when  sufficiently  compact  is  cut  into 
blocks  and  dried  on  an  absorbent  surface  of  plaster  of 
Paris  in  a  current  of  warm  air.  It  is  important  that  the 
temperature  of  the  moist  starch  be  not  raised  above  60°  C. 

In  another  process  the  milky  liquid  is  run  upon  an  inclined 
settling  floor,  and  made  to  run  slowly  back  and  forth 
toward  the  lower  end  of  the  room.  The  starch  is  deposited 
and  the  clear  water  run  off  at  the  lower  end.  Sometimes 
alkali  is  not  used,  but  the  germ  of  the  corn  is  mechanically 
removed  before  the  starchy  part  of  the  corn  is  ground. 

In  making  wheat  starch  the  softened  grain  is  sometimes 
ground  and  then  allowed  to  ferment  in  large  tanks  at  20°  C. 
for  14  days,  with  frequent  stirring.  By  the  fermentation 
which  takes  place  the  gluten  is  attacked  and  the  starch 
grains  are  set  free.  The  impure  liquid  is  drawn  off  and  the 
starchy  mixture  is  poured  through  revolving  sieves  or  made 
to  pass  through  the  meshes  of  hempen  sacks.  The  subse- 
quent operations  are  like  those  above  described. 

By  another  process  wheat  flour  is  mixed  with  water,  and 
the  dough  is  washed  repeatedly  in  bags  under  a  jet  of  water. 
Starch  is  obtained  from  the  water  by  running  it  into  settling 
tanks,  and  the  gluten  which  remains  in  the  bags  may  be 
utilized  for  making  macaroni. 

Experiment  70.  Mix  a  handful  of  flour  with  water,  and 
place  the  dough  in  a  cloth  bag,  and  hold  under  a  stream  of 


148  SANITARY   AND   APPLIED   CHEMISTRY 

running  water,  kneading  constantly  with  the  hands.  The 
starch  will  be  carried  away  with  the  water  and  the  gluten 
will  remain  in  the  bag.  Dry  the  contents  of  the  bag,  and 
examine  its  structure. 

The  insoluble  proteids  of  wheat  obtained  by  kneading  a 
dough  of  wheat  flour  in  a  stream  of  water  consist  of  about 
75  %  of  true  gluten  (gliadin  and  glutenin),  together  with 
small  percentages  of  non-gluten  proteids,  mineral  matter, 
fat,  starch,  fiber,  and  other  non-nitrogenous  matter.1 

Experiment  70  a.  As  the  value  of  a  flour  for  baking 
bread  depends  on  the  amount  of  gluten  present,  the  follow- 
ing method  has  been  used  to  compare  the  gluten-content  of 
flours.2  Place  10  g.  of  flour,  wet  with  an  equal  weight 
of  water,  in  a  porcelain  dish,  and  work  into  a  ball  with  a 
spatula,  taking  care  that  none  adheres  to  the  dish.  Allow 
the  ball  to  stand  for  an  hour,  then  knead  it  with  the  hand 
in  a  stream  of  cold  water  until  the  starch  and  soluble  mat- 
ter are  removed.  Allow  the  ball  of  gluten  to  remain  in 
cold  water  for  an  hour,  then  roll  into  a  compact  ball  with 
the  hands,  place  in  a  watch  glass,  and  weigh ;  this  is  moist 
gluten.  Dry  for  24  hours  on  a  water  bath  and  again  weigh, 
and  then  record  the  weight  as  that  of  dry  gluten. 

SUBSTANCES  RELATED  TO  STARCH 

Dextrin  (C6H100S)  is  a  substance  that  suggests  gum  in  its 
properties,  and  indeed  it  is  put  upon  the  market  under  the 
name  of  British  gum.  Several  varieties  of  dextrin  exist, 
and  it  is  evident  from  a  study  of  their  composition  that 
they  may  result  from  the  breaking  down  of  the  starch 
molecule,  by  means  of  dilute  acids  or  ferments. 

Commercial  dextrin  is  made  either  by  heating  starch  or 
flour  to  a  temperature  of  210-280°  C.,  or  by  moistening  the 

1  Norton,  J.  Am.  Ch.  Soc.,  1906. 

2  Wiley,  «« Agric.  Analysis,"  Vol.  Ill,  p.  435. 


CELLULOSE,    STARCH,   DEXTRIN,   ETC.  149 

starch  with  a  mixture  of  dilute  nitric  and  hydrochloric  acid, 
slowly  drying  the  paste,  and  heating  it  to  a  temperature 
between  110°  and  159°  C. 

Dextrin  obtained  by  either  of  these  processes  is  a  white  or 
yellowish  powder.  As  it  is  mostly  of  the  variety  known  as 
erythrodextrin,  its  aqueous  solution  gives  a  brown  color 
with  iodine.  It  is  slightly  soluble  in  dilute  alcohol,  but 
insoluble  in  60%  alcohol.  The  brown  crust  on  the  outside 
of  a  loaf  of  bread  is  composed  mostly  of  dextrin.  Dextrin 
is  used  on  the  back  of  postage  stamps  to  make  them  adhe- 
sive. 

The  Gums  are  colloidal  bodies  occurring  in  the  juices  of 
plants.  They  either  dissolve  or  swell  up  when  brought  in 
contact  with  cold  water.  Some  of  the  more  important  gums 
are :  Gum  Arabic,  Gum  Tragacanth,  and  the  Pectin  of  un- 
ripe fruit.  Their  food  value  has  only  been  imperfectly 
studied. 

Inulin  (C6H1005)  is  a  starchlike  substance  found  in  chic- 
ory, potatoes,  artichokes,  elecampane,  dahlias,  and  dande- 
lion roots.  It  is  a  white  powder,  readily  soluble  in  boiling 
water,  and  converted  into  levulose  by  boiling  with  water  or 
acids. 

PHYSICAL    PROPERTIES    OF    STARCH 

Starch  is  really  made  up  of  little  grains,  those  of  different 
plants  being  of  different  size  and  shape,  and  showing  con- 
centric markings.  This  indicates  that  the  grains  are  built 
up  of  different  layers ;  that  is,  a  layer  of  true  starch  and 
then  a  layer  of  a  kind  of  cellulose.  These  grains  are  not 
soluble  in  cold  water,  alcohol,  or  ether,  so  they  are  not 
washed  away  when  the  plant  is  broken.  If  boiling  water  is 
poured  upon  the  starch,  or  if  starch  is  heated  to  from  70  to 
80°  C.,  the  grains  burst  and  the  whole  forms  a  gelatinous 
mass,  having,  when  dry,  the  stiffening  properties  with  which 


150  SANITARY   AND   APPLIED   CHEMISTRY 

we  are  familiar.  In  order  to  thoroughly  cook  starch  so  that 
it  shall  be  digestible,  it  should  be  noted  that,  at  some  time 
in  the  process,  is  should  be  heated  as  high  as  100°  C.  Boiled 
with  water  for  a  long  time,  the  starch  goes  into  solution, 
1  part  dissolving  in  50  parts  of  water.  In  the  process  of 
cooking  starchy  foods,  the  grains  are  ruptured,  and  in  this 
condition  they  are  much  more  easily  attacked  by  the  diges- 
tive fluids. 

Experiment  71.  Place  some  starch  in  a  test  tube  with  a 
little  water  and  shake  moderately,  then  filter  and  test  the 
filtrate  for  starch  by  adding  tincture  of  iodine  (see  Experi- 
ment 76).  If  there  is  no  blue  color,  how  is  this  accounted  for  ? 

As  all  starches  are  of  practically  the  same  composition, 
the  only  way  of  detecting  the  source  of  any  specimen  of 
starch  is  by  the  use  of  the  microscope.  Although  there 
are  so  many  varieties,  yet  the  grains  of  each  differ  from  the 
others  in  size  or  shape,  or  in  their  appearance  with  polarized 
light.  The  expert  can  thus  detect  adulterations  and  the 
substitution  of  a  cheap  starch  for  an  expensive  one.  For 
illustrations  of  the  different  starches,  see  Leach  (plates). 

CHEMICAL  PROPERTIES   OF   STARCH 

When  starch  is  heated  to  100°  C.  it  changes  gradually  to 
soluble  starch.  At  a  temperature  of  160°  to  200°  C.  it  is 
changed  to  dextrin  (C6H1003)n;  from  220°  to  280°  C.  it 
is  changed  to  pyrodextrin,  which  is  soluble  in  alcohol.  Of 
course  if  heated  still  higher,  it  is  decomposed  and  gives  off 
combustible  gases. 

Experiment  72.  Prepare  starch  from  potatoes  by  peeling, 
scraping  to  a  pulp,  putting  in  a  cloth  bag  with  water,  and 
squeezing  out  the  milky  juice.  Allow  this  to  settle  (not 
over  24  hr. ),  pour  off  the  clear  liquid,  and  dry  the  resi- 
due at  a  temperature  not  above  70°  C.  on  a  water  bath. 


CELLULOSE,   STARCH,   DEXTRIN,   ETC.  151 

Experiment  73.  Make  starch  from  corn  meal  and  from 
acorn  meal,  by  grinding  with  water  in  a  mortar  and  treating 
as  in  Experiment  72. 

Experiment  74.  Make  an  emulsion  of  green  bananas, 
and  prepare  starch  from  this,  as  above. 

Experiment  75.  Make  starch  paste  by  mixing  a  few 
grams  of  one  of  the  specimens  of  starch  prepared  above 
with  cold  water  and  pouring  this  into  100  times  as  much 
boiling  water  and  heating  for  a  short  time. 

Experiment  76.  Test  a  small  portion  of  this  starch  paste, 
after  cooling,  with  a  few  drops  of  tincture  of  iodin.  (This 
is  made  by  dissolving  iodin  in  alcohol.)  A  blue  color  in- 
dicates the  presence  of  starch. 

Experiment  77.  To  make  dextrin  (C6H1006)n,  heat  about 
20  g.  of  starch  very  cautiously  in  a  porcelain  evaporating 
dish,  with  constant  stirring.  The  temperature  should  be 
between  210°  and  280°  C. 

Experiment  78.  Another  method  of  making  dextrin  is  to 
moisten  about  10  g.  of  starch  with  dilute  nitric  acid, 
dry  the  paste  on  a  water  bath,  and  finally  heat  slightly 
above  100°  C. 

Experiment  79.  Dissolve  some  of  the  dextrin  made  above 
in  cold  water  ( characteristic  test) ;  add  to  this  solution 
an  excess  of  alcohol,  to  precipitate  the  dextrin,  filter,  and 
wash  with  alcohol. 

Experiment  80.     Prepare  Fehling's  solution  as  follows :  — 

(a)  Dissolve    34.639  g.  of  copper  sulfate  in  500  cc. 

of  water. 
(6)   178  g.  of  Rochelle  salts  and  30  g.  of  sodium  hy- 

droxid  are  dissolved  in  water  and  diluted  to  500  cc. 


152  SANITARY   AND   APPLIED   CHEMISTKY 

Experiment  81.  Test  a  portion  of  the  dextrin  made  in 
previous  experiments,  dissolved  in  water, 

(a)  for  starch  with  tincture  of  iodin, 
(&)  for  sugar  (dextrose)  with  the  Fehling's  solution, 
as  mentioned  below. 

By  the  action  of  dilute  acids  the  change  known  as 
hydrolysis  takes  place  in  the  starch,  and  dextrin  and 
maltose  are  at  first  produced ;  these  are  changed  by  pro- 
longed boiling  to  dextrose  (C6H1206). 

Experiment  82.  Fehling's  Test  for  Dextrose.  To  a  dilute 
solution  of  commercial  glucose,  contained  in  a  medium- 
sized  test  tube,  add  5  cc.  of  a  and  5  cc.  of  6,  and  boil  for 
a  few  minutes.  The  formation  of  a  yellowish  red,  or,  in 
case  of  an  excess  of  dextrose,  of  a  red  flocculent  precipitate 
of  cuprous  oxid,  Cu20,  indicates  dextrose. 

Experiment  83.  Conversion  of  Starch  to  Dextrose.  Use 
about  3  g.  of  the  starch  made  above;  mix  with  200  cc. 
of  water  and  20  cc.  dilute  HC1.  Heat  on  a  water  bath  in  a 
flask  for  2  hours,  or  boil  for  15  minutes.  Cool,  neutralize 
with  sodium  hydroxid,  and  test  a  portion  of  the  solution 
by  Fehling's  solution  for  dextrose. 

Many  ferments  like  the  ptyalin  of  saliva,  or  the  pancre- 
atic ferment,  change  starch  to  sugar  (dextrose). 

Experiment  84.  Filter  some  saliva,  and  digest  this  with 
starch  paste  in  a  test  tube,  kept  in  a  water  bath  at  a 
temperature  not  above  98°  F.  (36.6°  C.)  for  15  min.  Test 
half  of  the  solution  for  starch  and  the  other  half  for 
maltose  by  Fehling's  solution. 

If  starch  is  digested  with  the  diastase  of  malt,  what 
is  known  as  "hydrolysis"  takes  place  and  the  starch  is 
changed  to  maltose,  C^H^Ou  -f  H,0,  which  resembles 


CELLULOSE,    STARCH,    DEXTRIN,    ETC.  153 

dextrose.     The  action  of  malt  upon  starch  is  expressed  by 
the  equation :  — 

(CeH^Os^  +  H20  =  C6H1005  +  C^H^OU. 

Starch  Dextrin  Maltose 

Experiment  85.  Prepare  malt  extract  by  digesting 
coarsely  pulverized  malt  for  several  hours  with  enough 
alcohol  to  cover  it.  Filter  and  set  the  solution  aside. 
When  the  alcohol  has  evaporated,  dissolve  the  residue, 
which  contains  the  ferment  known  as  diastase,  in  water. 
Make  a  thin  starch  paste,  cool  to  about  62°  C.,  add  a  little 
of  the  diastase,  and  digest  for  15  m.  at  this  temperature. 
Test  a  portion  of  the  solution  for  starch.  If  it  is  still 
present,  continue  the  digestion,  but  if  it  is  all  converted, 
test  for  maltose  by  Fehling's  solution. 

Strong  nitric  acid  in  the  cold  acts  upon  starch,  producing 
several  nitroamyloses,  collectively  known  as  xyloidin. 
These  resemble  nitrocellulose  (see  p.  126). 


CHAPTER  XII 
BREAD 

WHETHER  we  consider  the  white  bread  of  the  American 
housewife,  the  black  bread  of  the  German  peasant,  the 
oatmeal  "  scones  "  of  the  Scotch  laborer,  or  the  corn  "  pone  " 
of  the  Southern  plantation,  each  is  a  valuable  nutrient  and 
a  staple  food  in  its  locality. 

Bread  consists  practically  of  flour,  with  the  addition  of  a 
little  salt  and  water,  mixed  into  a  paste  and  baked  before  a 
fire.  The  simplest  flour  is  that  made  by  the  natives  of 
many  countries,  by  grinding,  or  "braying,"  the  grain 
between  two  stones.  This  was  one  of  the  earliest  mortars 
used.  It  is  quite  probable  that  the  name  "  bread "  comes 
from  the  word  "  brayed, "  referring  to  this  method  of 
breaking  the  grain. 

There  are  two  general  methods  of  making  dough  light:  — 

1.  By  nonfermentation  methods. 

2.  By  fermentation  methods. 

BREAD   NOT    RAISED   BY   FERMENTATION 

There  are  a  large  number  of  methods  used  for  making 
dough  light  without  the  use  of  yeast.  Unleavened  bread 
is  the  simplest  form  of  this  food  and  is  made  without  any 
ae'ration,  by  mixing  the  flour  and  water  and  baking.  Ex- 
amples of  this  kind  of  bread  are  the  passover  cake  of  the 
Israelites,  the  sea  biscuit  and  hard  tack  used  on  shipboard 
and  in  the  army,  the  Scotch  oat  cake,  and  the  corn-meal 
"pone"  so  extensively  used  in  the  South.  Graham  and 
whole-wheat  flour  are  used  in  the  same  way,  thus  making 
a  bread  that  is  claimed  to  be  more  wholesome,  and  which 

154 


BREAD  155 

may  6e  kept  for  a  much  longer  time  than  the  ordinary 
raised  bread.  Unleavened  bread  is  not,  however,  considered 
as  appetizing  as  raised  bread,  but  has  the  advantage  that 
on  account  of  its  hardness  and  dryness  it  must  be  thoroughly 
masticated  and  mixed  with  the  saliva,  and  thus  becomes 
more  readily  digested. 

Many  processes  have  been  devised  for  making  the  dough 
light  without  the  use  of  yeast.  The  object  of  these  is  to 
shorten  the  time  and  labor  of  making  the  bread.  The  fol- 
lowing methods  may  be  noticed,  and  will  serve  to  show  that 
much  thought  has  been  devoted  to  the  subject. 

1.  By  mixing  Graham  flour  or  wheat  flour  with  water, 
or  milk,  and  beating  it  vigorously  for  some  time,  and  baking 
quickly  in  cast-iron  pans,  a  fairly  light  bread  results.     The 
raising  substance  in  this  case  is  the  air  that  is  entrapped 
in  the  dough.     Gems  and  muffins  are  made  in  this  way  in 
some  dietary  establishments. 

2.  A  modification  of  the  above  plan  is  to  mix  the  mate- 
rials with  snow,  and  then  bake  quickly  in  a  hot  oven.     In 
this  case  the  cook  depends  on  the  air  that  is  entrapped  in 
the  snow  crystals  to  raise  the  dough. 

3.  Eggs,  beaten  to  a  froth,  will  entangle  sufficient  air  to 
make  dough  very  light  and  spongy.     This  fact  is  taken 
advantage  of  in  the  making  of  sponge  cake. 

4.  Brandy,  wine,  or  any  liquor,  diluted,  may  be  used  in- 
stead of  the  water,  in  the  mixing  of  dough,  and  when  this  is 
baked  the  expansion  and  volatilization  of  the  alcohol  will 
raise  the  dough.      It  is  probable  that  very  little  of  the 
alcohol  will  remain  in  the  finished  product,  but  there  are 
some  objections  to  this  method,  both  on  account  of  its  ex- 
pense, and  because  of  the  flavor  of  the  liquor  that  remains. 

5.  Ammonium    carbonate    (NH4)2C08    is  an  extremely 
volatile   substance,  and  if  a  solution,  or  the  fine  powder, 
be  mixed  with  the  flour,  it  will,  as  it  escapes  in  the  process  of 


156  SANITARY   AND   APPLIED   CHEMISTRY 

baking,  raise  the  dough.  This  has  been  used  with  yeast, 
by  the  baker,  to  obtain  very  light  bread.  The  ammonia  salt 
is  also  used  to  overcome  any  excess  of  acids  due  to  the  over- 
fermentation. 

6.  Sodium  bicarbonate  (NaHC08),  when  heated,  gives  off 
a  part  of  its  carbon  dioxid  gas  aud  some  water ;  and  as  this 
escapes  it  will  render  the  dough  light.     There  is,  however, 
a  great  disadvantage  in  the  use  of  this  substance,  as  there 
remains  in  the  bread  sodium  carbonate,  an  alkaline  sub- 
stance that  renders  the  bread  unwholesome. 

7.  A  modification  of  this  process,  however,  will  give  an 
excellent  product.     If  the  baking  soda  is  used  with  mo- 
lasses, which  usually  contains  some  free  acid,  then  the  alkali 
is  neutralized,  and  carbon  dioxid  is  set  free,  and  the  material 
is  very  light.     This  is  taken  advantage  of  in  making  ginger- 
bread.    If  the  molasses  is  not  sufficiently  acid,  a  little  vine- 
gar may  be  added  to  it. 

8.  Aerated  bread,  as  made  by  Dr.  Dauglish,  was  intro- 
duced a  few  years  ago,  and  for  a  time  seemed  to  be  so 
popular  in  this  country  that  there  was  a  prospect  of  its 
replacing  the  other  varieties  that  were  on  the  market,  but 
it  has  not  found  favor  here  in  recent  years.     It  is  used  ex- 
tensively   abroad,   especially   in  London.      It  possesses  a 
characteristic  taste  that  is  entirely  different  from  that  of 
fermented  bread.      In  the  manufacture  of  this  bread  the 
flour  is  mixed  in  a  strong  iron  vessel,  provided  with  a  me- 
chanical stirer,  with  salt,  and  water  that  is  impregnated  with 
carbon  dioxid  gas.     The  dough  is  forced  out  of  the  apparatus 
by  the  pressure  of  the  gas,  and  is  molded  into  loaves,  that 
are  immediately  placed  in  the  oven.     The  vesiculation  is 
produced  by  the  carbon  dioxid  gas,  which,  in  its  efforts  to 
escape,  raises  the  dough.     There  is  no  chemical  change  in 
the  flour,  as  in  fermentation  methods  of  making  bread,  and 
so  none  of  the  flour  is  lost  in  the  process. 


BREAD  157 

9.  A  process  that  is  somewhat  allied  to  this,  but  one 
that  has  not  been  received  with  very  much  favor,  is  to  mix 
the  flour  with  baking  soda,  and  then  to  add  to  the  water 
that  is  to  be  used  in  the  mixing  of  the  bread  sufficient 
hydrochloric  acid  to  combine  chemically  with  the  soda ;  and 
in  this  way  there  would  be  left  in  the  bread  nothing  but 
common  salt,  in  accordance  with  the  equation  — 

NaHC03+HCl  =  NaCl+H20+C02. 

10.  By  the  use  of  sodium  bicarbonate  and  freshly  curdled 
sour  milk,  excellent  results  may  be  attained.     In  this  case, 
there  is  left  in  the  bread  sodium  lactate,  an  entirely  harm- 
less salt,  and  carbon  dioxid  gas  is  set  free.     Some  skill  is  of 
course  required  to  get  sufficient  soda  in  the  material  to  ex- 
actly combine  with  the  acid  of  the  milk.     One  teacup  of  sour 
milk  will  usually  neutralize  a  teaspoonful  of  baking  soda.   If 
the  milk  is  not  acid  enough  for  the  purpose,  it  may  be  acidi- 
fied still  further  by  the  addition  of  some  vinegar.     Biscuit 
and  cakes  are  not  only  raised  by  this  process,  but  they  are 
rendered  richer  by  the  fat  and  the  casein  of  the  milk.     If 
too  much  soda  is  added,  the  product  is,  of  course,  yellow, 
alkaline,  and  unwholesome.     The  equation  is  — 

NaHC03+C2H5OCOOH=C2H5OCOONa+H20+C02. 

Lactic  acid  Sodium  lactate 

11.  Sodium  bicarbonate  and  cream  of  tartar  are  often 
used  to  render  dough  light.     The  first  of  these   may  be 
mixed  with  the  flour,  and  the  latter  with  the  water  that  is 
used  in  mixing  the  dough,  or  both  may  be  sifted  and  mixed 
with  the  flour.     This  is  an  excellent  method,  as  the  only 
salt  remaining  in  the  bread  is  "  Rochelle  salt,"  a  compara- 
tively harmless  substance,  though  in  large  quantities  it  acts 
as  a  laxative.     The  proportions  of  each  substance  to  be  used, 
as  estimated  from  the  molecular  weight,  are  one  part  of 
sodium  bicarbonate  to  two  parts  of  cream  of  tartar.     As  the 


158  SANITARY   AND   APPLIED   CHEMISTRY 

powders  do  not  differ  very  much  in  bulk,  they  may  be 
measured  with  a  teaspoon.  The  equation  representing  the 
reaction  that  takes  place  is  as  follows :  — 

KHC4H406  +  NaHCOs  =  KNa  C4H406  +  CO,  +  H20. 

12.  By  the  use  of  baking  powders.  These  powders  are 
of  three  kinds :  — 

1.  Cream-of -tartar  powders. 

2.  Phosphate  powders. 

3.  Alum  powders. 

The  use  of  baking  powders  is  more  common  in  the  United 
States  than  abroad.  It  is  said  that  the  amount  consumed  in 
one  year  will  amount  to  more  than  50,000,000  pounds.  The 
only  thing  added  to  the  soda  and  cream  of  tartar  or  other 
substance  furnishing  the  "acid"  in  the  manufacture  of  a 
baking  powder  is  some  starch  or  flour,  which  is  known  as  a 
"  filler."  This  is  said  to  be  necessary  to  prevent  the  ingre- 
dients from  combining  too  soon.  In  all  the  powders  baking 
soda  is  used  to  afford  the  requisite  amount  of  carbon  dioxid 
gas,  the  only  difference  between  them  being  in  the  acid 
salt  or  chemical  used  to  set  it  free. 

It  is  but  fair  to  state  that  the  amount  of  available  carbon 
dioxid  obtained  from  a  powder  may  depend  not  only  on  the 
quality  of  the  constituents,  the  skill  with  which  they  are 
mixed,  and  their  correct  proportion,  but  also  largely  upon 
the  age  of  the  powder.  The  bicarbonate  of  soda  and  the 
acid  potassium  tartrate  in  the  cream-of-tartar  powders,  or 
the  bicarbonate  of  soda  and  the  sodium  or  ammonium  sul- 
fate,  or  the  alum,  in  the  so-called  alum  powder,  will  gradu- 
ally combine,  especially  if  they  are  not  absolutely  dry,  as 
long  as  powder  is  kept  in  stock,  and  so  the  strength  of  the 
powder  will  be  diminished.  Of  the  thirty-one  samples  of 


BREAD  159 

baking-powder  recently  examined  by  the  author,  six  were 
cream-of-tartar  powders,  two  phosphate  powders,  fifteen 
alum-phosphate  and  eight  alum  powders.  The  amount  of 
available  carbon  dioxid  varied  from  1.41%  to  15.29%. 

12.  Tartrate  powders  consist  of  acid  potassium  tartrate 
or  tartaric  acid,  sodium  bicarbonate,  and  flour  or  starch. 
The  tartrate  is  made  from  "  argols,"  that  are  collected  in 
the  bottom  of  wine  casks  in  the  process  of  fermentation. 
The  value  of  a  baking  powder  depends  on  the  per  cent  of 
carbon  dioxid  gas  that  is  set  free  when  the  powder  is  put 
into  water.  The  reaction  is  the  same  as  shown  in  No.  11. 

Experiment  86.  To  show  the  evolution  of  carbon  dioxid 
from  a  baking  powder,  place  some  of  it  in  a  250  cc.  flask, 
provided  with  a  cork  through  which  passes  a  delivery  tube 
having  its  outer  end  below  the  surface  of  100  cc.  of -lime 
water  placed  in  a  beaker.  When  water  is  added  to  the 
baking  powder,  the  gas  is  rapidly  evolved  and  produces  a 
precipitate  in  the  lime  water :  — 

Ca(OH)2  +  C02  =  CaC03  +  H20. 

Experiment  87.  Test  a  baking  powder  for  flour  or  starch 
as  mentioned  in  Experiments  75  and  76. 

A  powder  of  the  cream-of-tartar  class  by  a  complete 
analysis  would  show  the  following  constituents : l  — 

PEE  CENT 

Total  carbon  dioxid  (C02) 12.25 

Sodium  oxid  (Na^-D) 11.03 

Potassium  oxid  (K20) 11.71 

Calcium  oxid  (CaO) .19 

Tartaric  acid  (C4H406) 35.14 

Sulfuric  acid  (S08) .  .12 

Starch 18.43 

Water  of  combination  and  association,  by  difference     .        .        11.13 

100.00 
1  Bui.  13,  Ft.  5,  U.  S.  Dept.  Agric.,  Div.  Chem. 


160  SANITARY   AND   APPLIED  CHEMISTRY 

The  available  carbon  dioxid  was  found  to  be  11.13%. 
This  powder  would  then  be  made  from  about  25  parts  of 
sodium  bicarbonate,  50  parts  of  cream  of  tartar,  and  25  parts 
of  starch.  The  small  quantities  of  other  substances  are 
accidental  impurities  in  the  chemicals  used.  Sometimes  a 
little  ammonium  carbonate  is  used  with  the  above  powder. 
As  this  is  really  a  mixture  of  ammonium  carbamate  and 
carbonate,  the  reactions  at  first  would  be  :  — 

NH4C02NH2  ==  2  NH3+  C02. 

Ammonium  Carbamate    Ammonium  Carbonate 


and  (NH4)2C03  =  2  NH8  +  H20  +  C02. 

Therefore  the  ammonia  salt  is  entirely  volatilized  by  the 
heat  of  the  oven. 

Experiment  87  a.  To  test  a  baking  powder  for  ammonium 
carbonate,  place  about  15  g.  in  a  beaker,  and  over  this  put 
a  watch  glass  carrying  on  its  under  side  a  moistened  slip 
of  red  litmus  paper.  If  the  beaker  is  warmed  carefully 
on  an  iron  plate  or  stove,  the  ammonia,  if  present,  will, 
after  some  time,  color  the  paper  blue. 

Experiment  87  b.  To  test  for  tartaric  acid  or  a  tartrate 
in  a  baking  powder,  place  about  10  g.  in  a  beaker,  add  water, 
and  after  a  short  time  filter  off  the  starch  and  insoluble  ma- 
terial. To  the  filtrate  add  a  little  copper  sulfate  solution 
and  some  sodium  carbonate,  and  boil  the  solution  for  a  few 
minutes.  Filter  off  any  copper  hydroxid  that  may  be 
present  and  dilute  the  filtrate  about  four  times.  If  the 
solution  is  a  distinct  blue,  especially  after  adding  more 
sodium  carbonate  and  boiling  again  and  filtering,  this  indi- 
cates the  presence  of  tartrates.1 

13.  Phosphate  powders  are  made  from  the  acid  phos- 
phate of  lime,  —  often  called  superphosphate,  —  sodium 

1  Bailey  and  Cady's  "  Qualitative  Analysis,"  p.  248. 


BREAD  161 

bicarbonate,  and  starch.  The  phosphate  is  made  by  the  ac- 
tion of  sulfuric  acid  on  bones,  consequently  it  sometimes 
contains  a  little  calcium  sulfate,  but  a  small  quantity  is  not 
considered  an  adulteration.  The  reaction  that  takes  place 
is  as  follows  :  — 

CaH4(P04)2  +  2  NaHC03  =  CaHP04  +  Na-jHPO,  +  2  C02 

+  2H20. 

The  substances  that  are  left  in  the  bread  are  considered 
about  as  harmless  as  the  Rochelle  salts,  and  are  by  some 
thought  to  be  of  actual  value  to  the  system.  On  analy- 
sis these  powders  are  shown  to  have  the  following  com- 
position : l  — 

PEE  CENT 

Total  carbon  dioxid  (C02) 13.47 

Sodium  oxid  (Na20) 12.66 

Potassium  oxid  (K2O) .31 

Calcium  oxid  (CaO) 10.27 

Phosphoric  acid  (P205) 21.83 

Starch 26.41 

Water  of  combination  and  association,  by  difference      .        .        15.05 

100.00 

Available  carbon  dioxid  12.86.  This  powder  would  be 
made  up  of  about  the  following  ingredients :  — 

PER  CENT 

Sodium  bicarbonate 26 

Acid  calcium  phosphate 37 

Starch 27 

Water  of  association,  &c.      .        . 10 

Experiment  88.  To  test  for  phosphoric  acid,  ignite  about 
6  g.  of  the  powder  in  a  porcelain  dish,  heat  the  residue 
with  nitric  acid,  dilute,  and  filter.  To  the  filtrate  add  am- 
monium molybdate,  and  warm  (do  not  boil),  when  the  for- 
mation of  an  abundant  yellow  precipitate  of  ammonium 

13,  Pt.  5,  U.  S.  Dept.  Agric.,  Div.  Chem. 


162  SANITARY   AND   APPLIED  CHEMISTRY 

phosphomolybdate  shows  the  presence  of  phosphoric  acid. 
It  should  be  remembered  that  the  ash  of  flour  will  show  a 
small  quantity  of  this  acid. 

14.  Alum  powders  are  often  mixed  with  phosphate  pow- 
ders, and  indeed  Professor  Mallet  states  that  he  finds  that 
this  is  usually  the  case.  The  alum  used  is  ammonia  alum, 
if  this  is  the  cheapest,  though  sometimes  "  cream-of-tar- 
tar  substitute  "  (calcined  double  sulfate  of  aluminum  and 
sodium)  is  used.  If  alum  is  used,  the  equation  would  be  — 

2  NH<A1(S04)2  _}_  6  NaHC03  =  2  A1(OH)3  +  3  Na^ 

+  (NH4)2S04  +  6  CO,. 

The  analysis  of  a  powder  of  this  class  shows  the  follow- 
ing constituents : 1  — 

PER  C«?rr 

Total  carbon  dioxid  (C02") •          7-90 

Sodium  oxid  (Na-jO) 6.99 

Calcium  oxid  (CaO) .12 

Aluminum  oxid  (A^Os)         .......          3.65 

Ammonia  (NH8)  i          1.02 

Sulfuric  acid  (SO8) 10.11 

Starch  45.41 

Water  of  combination  and  association,  by  difference    .        .        24.80 

100.00 
Available  carbon  dioxid 6.41 

This  powder  would,  therefore,  be  made  from  about  the 
following  constituents :  — 

PisC/Kirr 

Sodium  bicarbonate 21 

Ammonia  alum  (anhydrous)  .......  16 

Starch 45 

Water  of  crystallization  and  association         ....  19 

In  this  particular  powder  the  amount  of  available  carbon 
dioxid  is  low,  but  this  is  probably  because  the  powder  had 

1  Loc.  cit. 


BREAD  163 

been  in  stock  for  some  time.     Alum  powders  will  give  as 
much  available  carbon  dioxid  as  any  others. 

Many  experiments  have  been  made  to  decide  exactly  what 
is  left  in  the  bread  when  alum  and  phosphate  powder  is 
used.  From  these  investigations  it  is  shown  that  the 
powder  which  contains  enough  phosphate  to  combine  with 
the  alum  is  a  better  powder  than  the  one  consisting  of 
alum  alone.  This  is  so  because  the  phosphate  is  less 
liable  to  be  soluble  than  the  hydrate  of  aluminum.  It  was 
also  proven  that  the  interior  of  a  loaf  of  bread  seldom 
reaches  the  temperature  of  100°  C.,  and,  on  this  account,  the 
aluminum  hydrate  will  not  be  dried  sufficiently  to  render  it 
insoluble.  Professor  Mallet  says :  "A  part  of  the  aluminum 
unites  with  the  acid  of  the  gastric  juice  and  is  taken  up 
into  solution,  while  at  the  same  time  the  remainder  of  the 
aluminum  hydroxid,  or  phosphate,  throws  down,  in 
insoluble  form,  the  organic  substance  constituting  the 
peptic  ferment.  " l  From  experiments  made  upon  himself, 
he  concludes  that  aluminum  hydroxid  taken  into  the  system 
tends  to  produce  indigestion. 

Experiment  89.  To  test  for  sulfuric  acid,  ignite  about 
10  g.  of  baking  powder  in  a  porcelain  or  platinum  dish)  cool, 
and  boil  in  a  beaker  with  strong  hydrochloric  acid  until 
nearly  all  dissolved ;  dilute  with  water,  filter,  heat  nearly  to 
boiling,  and  add  barium  chlorid.  The  formation  of  a  fairly 
abundant  precipitate  of  BaS04  indicates  sulfuric  acid. 

Experiment  90.  If  sulfuric  acid  has  been  found,  alumina 
is  probably  also  present.  To  test  for  this,  apply  the 
logwood  test  mentioned  in  Experiment  95. 

Experiment  91.  Another  test  for  aluminum  salts  in 
baking  powders,  that  may  be  applied  even  in  the  presence 

1  Loc.  cit. 


164  SANITARY   AND   APPLIED   CHEMISTRY 

of  phosphates,  is  to  burn  about  2  g.  of  the  powder 
in  a  porcelain  or  platinum  dish,  extract  the  ash  with 
boiling  water,  and  filter.  Add  to  the  nitrate  enough 
ammonium  chlorid  solution  so  that  the  mixture  shall 
smell  distinctly  of  ammonia.  The  appearance  of  a  white, 
flocculent  precipitate,  especially  on  warming,  indicates  the 
presence  of  alumina.  The  equation  is  — 

Na2Al204  +  2NH4C1  +  4  H20 

=  2A1(OH)3  +  2NH4OH  -f  2  NaCl. 

Calcium  phosphate  would  be  insoluble  in  the  water, 
and  alkaline  phosphates  would  be  precipitated  only  when 
alumina  was  present.1 

Experiment  92.  To  test  for  alum  in  cream  of  tartar,  add 
to  the  sample  an  equal  quantity  of  sodium  carbonate,  burn 
the  mixture,  and  treat  the  ash  as  in  the  preceding  experiment. 

Experiment  92  a.  As  cream  of  tartar  is  often  adulter- 
ated with  calcium  phosphate,  to  test  for  this  impurity,  ignite 
a  sample  of  the  cream  of  tartar  and  proceed  as  in  Experi- 
ment 88. 

Experiment  93.  Ammonium  carbonate  may  be  detected  in 
a  baking  powder  by  mixing  it  with  a  little  water,  and  sus- 
pending in  the  beaker,  which  should  be  covered  with  a 
watch  glass,  a  piece  of  moistened  red  litmus  paper.  After 
a  time  this  will  become  blue  if  ammonia  is  present. 

It  is  essential  that  all  the  ingredients  of  which  a  baking 
powder  is  composed  should  be  well  dried  before  mixing. 
The  reason  for  this  is  obvious,  as  without  it  a  partial  com- 
bination is  liable  to  take  place  continuously.  Of  course 
there  is  a  temptation  to  add  more  starch  than  is  essential, 
but  an  amount  of  not  over  20  to  25  %  is  not  considered 
excessive,  and  less  than  this  is  sufficient  for  the  purpose. 

1  Leach,  31st  Ann.  Rep.,  Mass.  Styte  Bd.;- Health,  1899,  p.  638. 


BKEAD  165 

An  excellent  powder  for  domestic  use  may  be  made  as  fol- 
lows :  — 

LB. 

Cream  of  tartar,  fully  dried 1 

Cornstarch J 

Baking  soda \ 

These  materials  can  be  bought  at  a  moderate  price,  and 
should  be  dried  separately  and  well  mixed,  and  then  kept 
in  a  dry  place. 

Experiment  94.  To  test  for  lime  in  a  sample  of  cream  of 
tartar,  in  the  absence  of  phosphates,  ignite,  dissolve  the  ash 
in  water,  with  a  little  HC1,  filter,  and  add  an  excess  of 
ammonium  hydroxid,  and  a  few  drops  of  ammonium  oxalate. 
The  formation  of  a  white  precipitate  indicates  the  presence 
of  lime  (see  Experiment  92  a). 

BREAD   RAISED   BY  FERMENTATION 

Raised  bread  is  usually  made  from  wheat  or  rye  flour, 
which  is  made  into  a  paste  with  water,  salt,  and  yeast. 
There  are  several  ways  in  which  the  ferment  may  be  used. 

(a)   The  first  of  these  methods  is  by  the  use  of  yeast. 

(6)   The  second  is  by  the  use  of  "  leaven, "  or  sour  dough. 

(c)  The  third  is  commonly  known  as  the  "  salt-rising  " 
process. 

In  all  of  these  processes,  however,  the  yeast  germs 
bring  about  the  fermentation,  the  only  difference,  as  will  be 
seen  later,  being  the  source  from  which  the  ferment  comes. 

A.    THE   USE  OF  YEAST 

In  the  ordinary  method  the  yeast  is  mixed  with  a  little 
warm  (  not  hot )  water  and  flour,  or  potatoes  and  salt,  and 
thus  what  is  called  "  sponge  "  is  made.  This  is  allowed  to 
rise  for  some  hours,  and  to  it  is  added  more  flour,  and 
water  or  milk.  Fermentation  proceeds,  with  a  continual 


166  SANITARY   AND   APPLIED   CHEMISTKY 

evolution  of  gas.  The  gluten  which  is  in  the  dough 
retards  the  escape  of  the  carbon  dioxid,  and  the  tension  of 
the  warm  gas  expands  the  little  cells;  then  the  dough  is 
puffed  up  and  becomes  light  and  spongy.  It  is  then 
molded  into  loaves,  and  the  loaves  are  set  in  a  warm  place 
till  the  expansion  of  the  gases  has  raised  them  somewhat, 
and  it  is  then  baked  in  an  oven  heated  to  a  temperature  of 
from  350°  to  570°  F.  The  oven  should  not  be  too  hot  at 
first,  as  in  this  case  the  crust  that  is  formed  will  prevent 
the  interior  of  the  loaf  from  being  fully  baked,  or  it  will 
cause  the  loaf  to  crack  open  in  an  unsightly  way  from  the 
expanding  gases. 

Yeast  was  known  to  the  ancient  Egyptians,  and  from 
them  the  Greeks  and  Romans  learned  its  use.  In  the 
raising  of  bread  the  conditions  are  favorable  first  for  the 
breaking  up  of  the  starch  by  the  diastase  of  the  flour  into  a 
variety  of  sugar,  and  second,  by  the  action  of  yeast  a  part 
of  the  sugar  is  changed  into  carbon  dioxid  gas  and  alcohol. 
This  is  represented  by  the  following  equations :  — 

4 

C6H1005  +  H20  =  CaHuQeJ  C^Oe  =  2  C2H60  +  2  C02. 

Starch  Sugar  Alcohol 

Yeast  requires  for  its  growth  sugar,  nitrogenous  com- 
pounds, and  mineral  salts. 

Much  time  and  study  has  been  given,  by  chemists,  to  the 
cultivation  of  pure  yeasts,  and  to  the  cultivation  of  those 
varieties  best  adapted  to  bread  and  beer  making.  The 
variety  best  adapted  to  bread-making  is  said  to  be  Saccharo- 
myces  cerevisice. 

Brewers'  yeast,  which  is  one  of  the  best  to  use  for 
making  bread,  should  be  fresh  and  not  soured.  Compressed 
yeast  is  made  from  a  by-product  of  the  distilleries.  "  Top 
yeast"  or  bottom  yeast  may  be  used,  but  the  former  is 
considered  more  desirable  for  bread-making.  This  mate- 


BREAD  167 

rial  is  pressed  and  mixed  with  5  or  6  %  of  starch.  It  may 
be  wrapped  in  tinfoil,  while  still  somewhat  moist,  and  shipped 
in  a  refrigerator. 

For  domestic  use,  yeast  is  prepared  by  the  use  of  flour, 
water,  a  little  salt,  yeast,  and  some  mashed  potatoes.  To 
this  is  sometimes  added  water  in  which  hops  have  been 
boiled,  and  the  whole  is  allowed  to  ferment  for  about  6  hours. 
This  yeast  will  keep  well  in  a  cool  place,  but  in  a  warm 
place  it  ferments  rapidly  and  is  soon  sour.  A  yeast  can 
also  be  made  by  preparing  a  mixture  of  flour,  water,  and  salt 
and  then,  without  adding  the  yeast,  allowing  the  germs  to 
get  in  from  the  air.  After  a  few  days,  if  the  mixture  is  kept 
in  a  warm  place,  a  product  will  be  obtained  similar  to  the 
material  made  by  the  use  of  yeast. 

Sometimes  the  yeast  plant  is  mixed  with  corn  meal,  and 
the  dried  mass  is  put  upon  the  market  under  the  name  of 
"yeast  cakes."  These  cakes,  which  will  keep  almost  in- 
definitely, only  need  to  be  soaked  in  warm  water  to  be  ready 
for  use. 

B.     THE  USE  OF  LEAVEN 

In  the  use  of  the  leavening,  or  sour-dough  process,  which 
has  been  practiced  for  hundreds  of  years,  some  of  the  dough 
that  has  been  left  over  from  one  batch  of  bread  is  used  in 
raising  the  next.  "A  little  leaven  leaveneth  the  whole 
lump."  This  leaven  should  be  kept  in  a  cool  place,  lest  other 
microorganisms  besides  yeast  plants  get  into  the  dough,  and 
even  then  there  is  often  a  secondary,  or  lactic,  fermentation, 
so  that  the  resulting  bread  is  sour,  or  has  a  disagreeable 
taste.  Since  compressed  yeast  cakes  are  to  be  purchased 
almost  everywhere,  this  process  of  raising  bread  is  not  used 
as  much  as  formerly.  It  is  chiefly  used  in  the  raising  of  rye 
bread  and  other  coarse  forms  of  breadstuff s. 


168  SANITARY   AND   APPLIED   CHEMISTRY 

C.     THE   SALT -RISING  PROCESS 

The  salt-rising  process  depends  on  preparing  a  favorable 
medium  in  which  the  yeast  germs  will  grow,  and  then 
allowing  them  to  get  into  the  dough  from  the  air,  or  from 
the  ingredients  used  in  making  the  sponge.  The  bread 
is  started  by  the  use  of  flour,  or  corn  meal,  warm  milk, 
and  salt.  The  meal  begins  to  ferment  after  a  short  time, 
if  kept  in  a  warm  place,  but  the  fermented  material  will 
not  have  the  same  taste  and  odor  as  the  sponge  from  yeast, 
as  various  "wild  yeasts"  are  sure  to  be  present.  It  is 
probable  that  lactic  and  butyric  fermentation  also  take 
place  to  some  extent.  Although  salt,  in  any  quantities 
above  1.4  %,  retards  alcoholic  fermentation,1  yet  as  it  even  to 
a  greater  extent  retards  the  growth  of  foreign  ferments,  such 
as  lactic  and  certain  "  wild "  ferments,  it  is  probable  that 
its  addition  is  an  advantage,  on  the  whole,  if  this  method 
of  fermentation  is  used.  Salt-rising  bread  is  finer  grained 
than  yeast  bread,  and  has  a  peculiar  and  characteristic  odor, 
which  is  due,  no  doubt,  to  the  lactic  fermentation  which  has 
taken  place. 

CAUSES   THAT   AFFECT   FERMENTATION 

Organic  acids  assist  fermentation. 

Mineral  acids  will  destroy  the  ferment. 

Alkalies  stop  fermentation. 

Twenty  per  cent  of  alcohol  stops  fermentation. 

Drying  does  not  stop  fermentation. 

Boiling  destroys  the  ferment. 

A  low  temperature  hinders  fermentation,  but  does  not 
destroy  the  ferment. 

Alcoholic  fermentation  takes  place  best  at  a  temperature 
of  from  9°  to  25°  C.  (from  48.2°  to  77°  F.).  The  yeast  plant 
grows  very  rapidly,  by  a  process  of  "  budding " ;  so  that 
1  Jago,  "  The  Science  and  Art  of  Bread  Making,"  p.  217. 


BKEAD  169 

often  one  cell  will  multiply  to  eighty  in  9  hr.  Above 
30°  C.  butyric  fermentation  sets  in,  and  the  products  are 
still  further  changed.  Ferments  may  be  kept  out  of  a 
fermentable  liquid,  or  medium,  by  first  sterilizing  it  by  heat, 
then  protecting  it  with  a  wad  of  sterilized  cotton,  or  even 
by  a  capillary  tube  that  is  very  much  twisted. 

If  the  process  of  fermentation  is  allowed  to  go  too  far, 
the  sugar,  or  some  of  it,  is  further  decomposed  into  lactic 
acid,  thus :  — • 

C6H1206  =  2  C3H603, 

Lactic  acid 

and  the  dough  becomes  sour.  This  may  also  take  place, 
in  some  cases,  by  the  formation  of  other  acids  in  the  mass, 
as  the  moist  dough  is  a  good  medium  for  the  growth  of 
various  ferments  besides  the  yeast  plant. 

Some  of  the  most  important  things  to  be  noted  in  the 
making  of  good  bread:  — 

1.  Thorough  kneading,  in  order  to  distribute  the  sponge 
or  yeast  well  through  the  mass.     Lack  of  attention  to  this 
will  cause  the  bread  to  be  coarse  grained,  and  to  have  large 
holes  distributed  irregularly  through  it. 

2.  The  dough  should  be  allowed  to  rise  sufficiently,  so 
that  the  carbon  dioxid  gas  and  the  alcohol  that  are  formed 
in  the  process  of  fermentation  may  have  an  opportunity  to 
raise  the  loaf.     In  this  process,  the  soluble  albumen  and 
globulin  of  the  flour  become  insoluble,  and  can  no  longer 
be  separated  from  the  starch.     It  is  probable  that  some  of 
the   gliadin   is   rendered   soluble.      The  starch  is  partly 
changed  to  soluble  carbohydrate,  and  partly  changed  to 
carbon  dioxid  and  alcohol. 

3.  In  the  process  of  baking,  the  heat  should  not  be  too 
great,  at  first,  but  time  should  be  given  for  the  dough  to 
dry  throughout  the  whole  mass,  for  the  cell  walls  to  become 
firm,  and  for  the  starch  to  become  well  cooked.     As  this 


170  SANITABY   AND  APPLIED   CHEMISTRY 

heating  goes  on,  while  the  inside  of  the  loaf  is  not  usually 
heated  above  100°  C.,  the  outside  will  gradually  get  hotter, 
dextrin  and  some  caramel  will  be  formed,  and  the  yeast 
cells  will  be  killed  by  the  heat.  Baking  renders  the  starch 
more  soluble,  and  hence  digestible.  The  dextrin  that  is 
formed  is  sweeter  than  starch,  and  as  it  is  more  soluble, 
there  is  reason  in  the  belief  that  it  is  a  better  food  for 
invalids  than  the  crumb.  It  is  also  necessary  to  masticate 
toast  thoroughly ;  that  is,  if  it  is  eaten  dry,  so  the  process 
of  digestion  will  be  further  assisted. 

Before  putting  the  loaves  into  the  oven,  they  are  some- 
times moistened  on  the  surface,  to  assist  in  the  prompt 
formation  of  a  crust  that  shall  restrain  the  loaf  in  its  ten- 
dency to  expand  too  rapidly.  If  steam  is  injected  into  the 
oven  during  baking,  it  produces  a  glazed  surface  on  the  loaf. 
The  steam  given  off  from  the  bread  when  it  is  first  put  into  the 
oven  acts  in  the  same  way.  In  baking,  the  heat  also  expands 
the  gases  given  off,  and  this  assists  in  puffing  up  the  dough. 

4.  The  process  of  fermentation  should  not  be  allowed 
to  go  too  far.  If  we  knew  the  exact  amount  of  lactic 
acid  formed  in  any  case,  we  might  add  sufficient  sodium 
bicarbonate,  known  as  "  baking  soda,"  to  neutralize  it,  but 
as  we  cannot  in  practice  do  this,  it  is  better  to  regulate  the 
temperature  carefully,  so  that  the  dough  does  not  get  too 
light.  If  too  much  baking  soda  is  added,  the  loaf  will  be 
yellow  in  color,  alkaline,  and  unwholesome. 

In  the  process  of  baking,  bread  will  lose  from  15  to 
20  %  of  its  weight.  This  loss  is  due  to  the  escape  of 
carbon  dioxid  gas,  water,  and  alcohol.  Elaborate  attempts 
have  been  made  to  collect  the  alcohol  that  escapes  during 
the  process,  but  they  have  so  far  been  failures.  There  is 
no  small  amount  lost,  however,  as  Liebig  estimated  that  in 
Germany  alone  12,000,000  gal.  of  alcohol  disappeared  yearly 
in  this  industry.  There  remains  in  the  fresh  bread,  after 


BREAD  171 

baking,  about  2  parts  of  alcohol  per  1000,  and  after  a  week 
this  amount  is  diminished  to  1  part  per  1000.  One  author 
estimated  that  40  2-lb.  loaves  contained  as  much  alcohol 
as  a  bottle  of  port  wine. 

A  good  method  for  testing  the  heat  of  the  oven  is  to  throw 
into  it  some  dry  flour,  and  if  it  soon  becomes  brown  the 
temperature  is  sufficiently  high.  The  flour  should  not  burn, 
of  course,  bat  dextrin  should  be  formed.  The  question 
naturally  arises,  Why  does  not  the  bread  burn  at  this  high 
temperature  ?  If  we  remember  the  large  amount  of  moisture 
and  alcohol  that  are  evaporated  during  the  process  of  bak- 
ing, it  is  easy  to  see  that  for  a  time,  at  least,  much  of  the 
heat  is  used  up  in  driving  off  these  substances,  and  it  is  not 
till  later  in  the  operation  that  the  temperature  is  high  enough 
to  change  the  starch  of  the  outside  of  the  loaf  into  dextrin. 

In  large  bakeries  the  oven  is  heated  to  a  temperature  a 
little  above  that  required  to  bake  the  bread  (390°F.)  at 
first,  and  when  the  bread  is  put  in  the  temperature  falls,  on 
account  of  the  amount  of  cold  material  that  has  come  into 
the  oven,  and  then  gradually  rises  again,  even  if  no  more 
fuel  is  added.  Just  before  a  batch  is  baked  more  fuel  is 
added,  to  raise  the  temperature  at  the  close  of  the  operation, 
and  to  prepare  the  oven  for  the  next  lot. 

In  the  old-fashioned  way  of  baking  in  a  brick  oven,  a  fire 
was  built  in  the  oven,  and,  when  the  bricks  became  hot,  the 
fire  was  removed,  the  ashes  swept  out,  and  the  bread  was 
baked  with  the  heat  that  the  walls  of  the  oven  had  re- 
tained. This  method  of  baking  is  still  used  on  a  large 
scale,  especially  in  England.  The  Dutch  oven,  an  iron  pot, 
with  a  cast-iron  cover,  which  is  kept  hot  by  coals  above  and 
below,  is  used  for  baking  where  no  better  appliance  is  at 
hand.  In  most  large  bakeries  crackers  are  baked  on  the 
swinging  shelves  of  a  horizontal  cylinder  that  slowly  moves 
above  a  smokeless  fire.  About  twenty  minutes  is  required 


172  SANITARY   AND   APPLIED   CHEMISTRY 

for  baking  a  batch,  which  is  put  into  the  oven  at  the  same 
point  where  the  previous  lot  was  removed.  The  swinging 
shelves  are  so  arranged  that  the  heat  is  uniformly  dis- 
tributed under  the  revolving  wheel,  and  by  a  mechanical 
arrangement  any  point  of  this  wheel  may  be  brought  in 
front  of  the  charging  door. 

That  there  is  a  difference  between  fresh  bread  and  that 
which  is  several  days  old  is  very  apparent.  What  this 
difference  is  was  for  some  time  a  question.  It  was  formerly 
said  that  this  difference  was  due  solely  to  the  loss  of  water, 
but  that  is  proved  not  to  be  the  case,  as  there  is  nearly  as 
much  water  in  bread  after  several  days  as  when  the  bread 
is  fresh,  and  if  stale  bread  is  reheated  it  becomes  for  the 
time  fresh  again.  It  has  been  suggested  that  in  fresh 
bread  some  free  water  is  present,  which  becomes  united 
with  the  starch  or  gluten  as  the  bread  grows  stale,  and  that 
reheating  sets  it  free  again.  It  has  also  been  stated  that 
the  difference  is  only  a  "  molecular  one. "  Stale  bread  still 
contains  about  45  %  of  water.  The  true  theory  may  be 
that  as  bread  dries  the  fibers  gradually  approach  nearer  to 
each  other  by  shrinkage,  and  the  walls  of  the  thousands  of 
pores  are  consolidated,  and  the  size  of  the  pores  is  thus 
increased.  When  the  stale  bread  is  heated,  expansion 
occurs ;  by  the  conversion  of  some  of  the  water  into  vapor, 
the  adhesion  between  the  fibers  is  broken  up,  drawing  them 
apart  in  the  direction  of  the  least  resistance,  producing  an 
apparent  diminution  in  the  porosity. 

A  great  impetus  was  given  to  the  baking  industry  by  the 
Vienna  Baking  Exhibit  at  Philadelphia,  in  1876.  Bread 
furnished  by  the  bakers  at  present  is  a  better  imitation  of 
the  domestic  bread,  and  hence  is  more  palatable,  than  that 
formerly  made. 

From  100  Ib.  of  flour  it  is  possible  to  make  135  to 
150  Ib.  of  bread,  or,  it  may  be  stated,  that  from  f  Ib. 


BREAD 


173 


of  flour  it  is  possible  to  make  1  Ib.  of  bread.  If  dry 
flour  contains  16  %  of  water,  when  this  is  made  into 
bread  it  gives  the  composition:  flour,  84  parts;  water,  16 
and  50,  making  150  parts.  The  water  is  retained  by  the 
gluten  cells.  A  flour  that  contains  only  a  little  gluten  will 
not  make  a  good  strong  dough.  Bakers  take  advantage  of 
this,  and  to  make  a  strong  dough,  that  will  rise  well,  they 
mix  hard  and  soft  wheat  in  such  proportions  as  will  give 
a  dough  that  is  rich  in  gluten.  When  considered  with 
reference  to  the  amount  of  gluten,  the  following  analysis  of 
bread  is  of  interest:  — 

PEE  CENT 

Water 40 

Gluten 7 

Starch,  sugar,  and  gum 51 

Salts _2 

100 

From  Bulletin  13,  Part  9,  of  the  Bureau  of  Chemistry, 
United  States  Department  of  Agriculture,  the  following 
analyses  are  quoted :  — 


H 

...    ..... 

g 

00 

x 

B 

H 

B 

ft  C*4 

w  -M 

£ 

H 

K 

^  OD"  BE 

I 

gee 

H^ 

H 

a 

ggsg 

1 

§  X 

gg 

B 

b 

m 

as  -x  b  B 

a  a  -  - 

S 

P-H  ^ 

W 

i 

<  o  om 

0 

o 

38.71 

8.87 

1.06 

.62 

.57 

1.19 

68.72 

Home-made  bread  .... 

38.02 

7.94 

1.95 

.24 

.56 

1.05 

56.75 

34.80 

8.93 

2.03 

1.18 

.69 

1.59 

58.40 

38.42 

8.68 

.66 

.62 

1.00 

1.84 

56.21 

Miscellaneous  bread  .    .    . 

84.41 

7.60 

1.48 

.80 

.49 

1.00 

56.18 

Biscuits  or  crackers.  .    .    . 

7.18 

10.34 

8.67 

.47 

.99 

1.57 

73.17 

Bolls         .             .... 

27.98 

8.20 

8.41 

.60 

.69 

1.81 

59.82 

Contrary  to  the  opinion  that  has  been  held,  recent  analyses 
show  that  white  bread  really  contains  more  proteids,  espe- 
cially those  that  can  be  absorbed,  than  "  whole  meal "  or 
Graham  bread. 


174 


SANITARY   AND   APPLIED   CHEMISTRY 


For  comparing  the  "  crumb "  and  the  "  crust, "  we  have 
the  following  analyses,  calculated  from  anhydrous  bread:  — 


NITROGE- 
NOUS 

DEXTRIN 

AND  SOL. 

STARCH 

SUGAR 

FAT 

STARCH 

WATER  IN 
ORIGINAL 
BREAD 

Crumb    .    . 

11.29 

14.9T 

4.17 

1.68 

67.87 

40.60 

Crnst  .     .    . 

10.97 

16.09 

4.15 

.71 

68.07 

18.00 

A  great  variety  of  products  is  now  put  on  the  market 
by  the  cracker  factories.  These  include  such  brands  as 
"  pilots,"  made  without  yeast,  but  with  hot  water,  lard,  flour, 
and  salt ;  "  sodas,"  made  by  the  use  of  flour,  yeast,  and  lard, 
or  cotton-seed  oil ;  "wafers,"  made  by  the  use  of  butter,  sugar, 
vanilla,  flour,  and  baking  powder ;  and  "  snaps,"  made  from 
sugar,  flour,  lard,  baking  powder,  and  ginger. 

Starch  alone  is  not  sufficient  to  sustain  life,  for  the  nitro- 
gen, to  assist  in  building  up  the  tissues  of  the  body,  must 
also  be  obtained  from  some  organic  source.  One  fact  not 
to  be  lost  sight  of  is  that  man  does  not  live  "by  bread 
alone."  He  does  make  use  of  a  large  amount  of  nitrogenous 
food,  in  the  shape  of  beef,  milk,  eggs,  etc. ;  so  it  is  not  ab- 
solutely necessary  that  the  wheat  or  other  grain  should 
furnish  sufficient  nitrogenous  material  to  sustain  life.  In  the 
modern  processes  of  milling,  the  first  and  second  grades  of 
flour  are  really  rich  in  proteids.  The  bran  that  man  may 
have  discarded  is  used  by  the  lower  animals  for  food,  and  so 
in  the  beef,  pork,  and  mutton  we  get  the  proteids  that  are 
necessary.  Man  chooses  to  allow  the  animal  to  do  this 
concentrating  for  him,  and  thus  he  has  the  advantage  of  a 
mixed  diet. 

Some  so-called  Infants'  Foods  are  principally  starch,  and 
when  fed  to  infants  are  practically  useless,  as  the  starch- 


BREAD  175 

converting  ferments  of  the  pancreatic  juice  are  not  secreted 
till  about  the  end  of  the  first  year.1 

Bread  must,  however,  be  regarded  as  one  of  the  most 
nutritious  of  foods.  It  yields  to  the  blood  a  large  quantity 
of  carbohydrates,  considerable  proteids  and  mineral  salts, 
and  but  very  little  fat.  When  it  is  eaten  with  butter,  the 
deficiency  of  fat  is  made  up ;  we  also  eat  bread  with  meat, 
and  thus  the  lack  of  proteids,  which  would  be  necessary  to 
make  bread  a  perfect  food,  is  supplied.  Bread  and  milk  is 
a  better  balanced  ration  than  bread  alone,  as  the  milk  fur- 
nishes both  proteid  and  fat  to  supplement  the  deficiency. 

Many  experiments  have  been  made,  and  much  has  been 
written,  on  the  relative  value  of  white  bread  and  bran,  Gra- 
ham, and  whole-wheat  bread.  Even  if  sometimes  the  whole- 
wheat bread  does  contain  more  proteids,  they  are  in  such  a 
form  that  they  cannot  be  readily  acted  upon  by  the  diges- 
tive juices  and  so  there  seems  to  be  a  less  absorption  of 
them  than  in  the  case  of  white  bread.  Artificial  digestion 
experiments  confirm  this  opinion.2  Then,  too,  the  coarser 
breads  are  liable  to  produce  some  irritation  in  the  intes- 
tines, and  this  prevents  perfect  digestion  and  absorption  of 
the  food. 

Many  attempts  have  been  made  to  perfect  a  flour,  richer 
in  proteids,  and  better  adapted  than  ordinary  flour  to  sustain 
animal  life.  Such  attempts  are  the  mixing  of  pease  meal 
and  of  casein  with  flour,  and  the  use  of  milk  in  making 
the  bread.  There  are  also  many  so-called  "  germ  flours  "  on 
the  market,  and  if  it  is  proved  that  they  are  well  absorbed, 
this  may  help  to  solve  the  problem. 

It  is  probably  true  that  the  second  grade  of  flour  will 
make  a  more  nutritious  bread  than  the  highest  "patent." 
If  stale  bread  is  rebaked,  it  becomes,  for  the  time,  fresh 

1  Cotton's  "Anatomy,  Physiology,  and  Hygiene  of  Childhood." 

2  Snyder,  U.  S.  Dept.  Agric.,  0.  Ex.  Sta.,  Bui.  101. 


176  SANITARY   AND   APPLIED   CHEMISTRY 

again.  It  is  a  well-known  fact  that  stale  bread  has  the 
reputation  of  being  more  wholesome,  and  this  is  founded  on 
reason,  because  fresh  bread  has  a  tendency,  when  masti- 
cated, to  roll  together  in  doughy  masses  that  are  not 
readily  attacked  by  the  digestive  fluids.  Stale  bread  retains 
its  porosity,  to  a  large  extent,  while  it  is  being  mixed  with 
the  saliva. 

In  addition  to  wheat  bread,  a  brown  bread,  made  from 
wheat  and  Indian  meal,  or  rye  and  Indian  meal,  is  much  in 
favor  in  some  localities.  The  addition  of  rye  or  wheat 
assists  very  much  in  the  raising  of  the  dough,  because  there 
is  not  sufficient  gluten  in  the  meal  to  make  a  strong  dough 
that  will  retain  the  gas  bubbles.  The  properties  of  flour 
from  the  other  grains  are  discussed  elsewhere. 

Bread  may  be  bad  from  several  causes.  Among  these 
may  be  mentioned  the  following :  — 

1.  It  is  bitter,  from  an  abnormal  growth  in  the  flour,  or 
from  the  grain  being  partly  spoiled. 

2.  It  is  heavy,  from  being  imperfectly  baked,  or  from  the 
use  of  poor  yeast,  or  from  not  being  allowed  to  rise  suffi- 
ciently before  being  placed  in  the  oven. 

3.  The  flour  may  be  deficient  in  gluten,  from  bad  milling, 
or  from  the  "  growing  "  of  the  wheat  before  it  was  ground. 
In  this  case  light  bread  cannot  be  made,  as  the  dough  does 
not  possess  sufficient  tenacity  to  cling  together  and  hold 
the  gases  that  are  evolved. 

4.  The  bread  may  be  sour  from   overfermentation,  or, 
what    amounts   to  the  same  thing,  from  allowing  the  fer- 
mentation to  proceed  at  too  high  a  temperature.     There  is 
no  excuse  for  this,  as  it  simply  denotes  carelessness  or 
ignorance. 

5.  Bread  may  be  moldy  if  it  is  kept  in  a  damp  place  or 
if  it  is  kept  too  long.     This  mold  is  due  to  the  growth 
of  microscopic  plants  that  find  the  moist  bread  a  fertile 


BREAD  177 

medium.  These  molds  may  be  white,  green,  orange,  or  black. 
They  are  supposed  by  some  to  be  poisonous  and  to  produce 
severe  disorders,  but  even  if  that  is  not  the  case  they 
render  the  bread  unfit  for  use. 

The  center  of  a  loaf  of  bread  is  sometimes  the  feeding 
ground  for  these  lower  organisms,  especially  in  very  warm 
weather,  because  the  heat  of  the  oven  has  not  been  sufficient 
to  entirely  sterilize  the  interior,  and  so  the  bread  spoils.  The 
texture  of  the  loaf  will  be  changed  so  that  it  will  be  stringy 
and  a  disagreeable  odor  is  emitted. 

6.  The  bread  may  be  of  a  dark  color,  though  not  made 
from  lower  grades  of  flour.  This  is  due  to  the  change  that 
has  taken  place  in  the  grain  or  in  the  flour  by  its  being  wet 
and  allowing  the  starch  to  change  to  dextrin,  gum,  or  sugar. 
This  is  practically  what  takes  place  in  the  malting  of  grains. 

ADULTERATION  OP  FLOUR  AND  BREAD ;  COMPOUND 

FLOUR 

The  most  common  adulteration  of  flour  in  the  United 
States  is  the  addition  to  it  of  other  flours,  especially  that 
of  corn  and  possibly  rice.  This  can  be  readily  detected  by 
the  use  of  the  microscope.  The  government  requires  all 
such  flours  to  be  labeled  "  Compound, "  and  to  pay  a  reve- 
nue tax  of  4  cents  per  barrel. 

As  white  bread  commands  a  better  price  than  dark,  and 
as  there  is  always  a  greater  demand  for  white  bread,  various 
attempts  have  been  made  to  make  a  white  bread  from  a  low 
grade  of  flour.  Substances  used  for  this  purpose  formerly 
constituted  the  chief  adulteration  to  which  flour  was  liable. 
In  Europe  copper  sulfate  and  alum  have  been  used,  but  in 
many  countries  their  use  is  now  prohibited  by  law.  Even 
so  small  a  quantity  as  1  part  of  copper  sulfate  in  10,000  parts 
of  flour  is  said  to  be  sufficient  to  enable  the  baker  to  make 


178  SANITARY  AND   APPLIED   CHEMISTRY 

a  white  bread  from  a  low  grade  of  flour.  The  use  of  this 
chemical  is  condemned  on  account  of  the  poisonous  nature 
of  the  salts  of  copper. 

Liebig  states  that  the  alum  makes  insoluble  the  gluten  that 
has  before  been  rendered  partially  soluble  by  the  acetic  and 
lactic  acids  that  were  developed  in  the  process  of  fermenta- 
tion. In  this  way  the  change  from  starch  to  dextrin  or 
sugar  is  arrested.  There  is  a  difference  of  opinion  as  to  the 
effect  of  alum  upon  the  system,  but  the  most  reliable  testi- 
mony is  that  as  the  loaf  is  not  heated  much  above  100  °  C. 
the  alumina  will  not  be  rendered  insoluble.  In  that  case  it 
will  go  into  the  circulation  and  thus  tend  to  injure  the  sys- 
tem. The  amount  of  alum  used  is  not  over  \\  to  3  ounces 
to  100  Ib.  of  flour.  It  is  stated  that  by  the  use  of  a  patent 
process  some  oxid  of  nitrogen  is  now  used  in  bleaching  flour. 

Experiment  94  a.  To  test  for  copper  sulfate  some  of  the 
bread  may  be  ignited  in  a  porcelain  dish  with  nitric  acid, 
and  the  ash  that  is  left  is  boiled  with  a  few  drops  of  nitric 
acid,  diluted  and  filtered.  To  one  half  of  the  filtrate  an 
excess  of  ammonium  hydroxid  is  added,  and  a  blue  colora- 
tion will  indicate  the  presence  of  copper.  The  other  half 
should  be  neutralized  with  sodium  hydroxid,  made  slightly 
acid  with  acetic  acid,  and  tested  by  means  of  potassium  f  erro- 
cyanid.  The  appearance  of  a  reddish  color  indicates  copper. 

Experiment  95.  To  detect  alum  in  flour,  the  logwood  test 
has  been  found  very  satisfactory.  Fifty  grams  of  flour  are 
mixed  with  50  cc.  of  distilled  water,  and  to  this  is  added 
5  cc.  of  a  freshly  prepared  logwood  solution,  and  the  whole 
is  made  alkaline  with  5  cc.  of  a  solution  of  ammonium 
carbonate.  With  as  small  a  quantity  of  alum  as  Tir^FO  the 
color  of  the  solution  will  be  lavender  blue,  instead  of  a  dirty 
pink.  It  is  well  to  set  the  mixture  aside  in  a  warm  place  for 
2  hr.,  and  notice  if  the  blue  color  is  permanent. 


BREAD  179 

Experiment  96.  To  test  for  alum  in  bread,  add  to  50  cc. 
of  water  5  cc.  of  the  logwood  solution  and  5  cc.  of  am- 
monium carbonate  solution.  Soak  about  10  g.  of  the  crumb 
in  this  for  5  minutes,  pour  out  the  liquid,  and  dry  the  bread 
at  a  gentle  heat.  If  alum  is  present  the  lavender  or  dark  blue 
color  will  appear,  but  if  the  bread  is  pure  it  will  turn  to  a 
dirty  brown  color. 

As  alum  is  not  often  used  in  flour  in  this  country,  these 
tests  may  be  made  with  some  of  the  "  self  -rising "  flours, 
which  are  liable  to  contain  alum,  or  upon  cakes  made  from 
this  flour. 

Ergot  is  sometimes  found  in  flour,  especially  in  that  made 
from  rye.  This  is  due  to  the  "  spurred  rye, "  as  it  is  called, 
or  really  to  a  fungus  growth  that  is  found  on  the  grain.  It 
is  poisonous,  and  sometimes  has  proven  injurious  to  the 
lower  animals. 

There  is  very  little  danger,  in  the  United  States  at  least, 
of  the  adulteration  of  flour  with  clay,  chalk,  terra  alba,  or 
any  such  materials. 

Recently  the  process  of  bleaching  flour  has  been  intro- 
duced. For  this  purpose  oxides  of  nitrogen  are  generally 
employed.  Electricity  is  frequently  used  in  the  production 
of  these  oxides.  The  object  of  bleaching  flour  is  to  enable 
the  miller  to  make  more  white  flour  from  the  grain. 
Opinions  are  divided  as  to  the  wholesomeness  of  flour 
treated  in  this  way. 


CHAPTER  XIII 
PREDIGESTED  AND  SPECIAL  FOODS 

BREAKFAST  foods  and  "  predigested  "  foods  have  recently 
been  introduced,  ostensibly  to  take  the  place  of  foods 
improperly  prepared,  and  to  assist  digestion.  That  there 
is  a  popular  demand  for  foods  of  this  kind  there  is  no  doubt, 
but  their  extended  use  is  only  another  illustration  of  the 
tendency  in  the  United  States  to  allow  some  one  else  to  do 
the  work  of  the  household  for  us,  even  though  the  food  thus 
prepared  may  be  expensive  and  unsatisfactory.  The  state- 
ments made  on  the  package  usually  have  nothing  to  do 
with  the  value  or  digestibility  of  the  food.  The  price  at 
which  they  are  sold  also  bears  no  relation  to  the  weight  of 
the  package  or  the  nutritive  value. 

Foods  for  infants  and  invalids  are  made  up  largely  of 
cereals  which  are  modified  by  application  of  heat,  by  digestion 
with  malt  or  diastase,  and  by  malting  the  cereal,  adding  cream 
or  milk,  and  evaporating.  Among  those  prepared  by  heat 
alone  may  be  mentioned  Blair's  and  Imperial  Granum ;  Mel- 
lin's  and  Horlick's  foods  are  representatives  of  the  class 
that  is  made  by  mixing  wheat  flour  with  malt  and  a  little 
potassium  carbonate,  moistening  with  water  and  heating  at  a 
fixed  temperature  for  several  hours.1  The  starch  of  the  flour 
is  by  this  process  changed  to  maltose  and  dextrin,  which  are 
soluble  substances.  In  making  the  malted  cream  foods,  the 

1  Canadian  Dept.  of  Inland  Rev.,  Bui.  69. 
180 


PEEDIGESTED   AND   SPECIAL   FOODS 


181 


flour  is  made  into  dough,  baked,  ground,  and  malted,  mixed 
with  cream,  and  evaporated  to  dryness  in  a  vacuum.  Foods 
of  this  class,  such  as  Malted  Milk  and  Nestle's  Pood,  are 
richer  in  fat  and  albumen  than  the  others  mentioned.1 

The  following  analyses  from  Konig  illustrate  the  differ- 
ence in  composition  between  some  of  these  foods  :  — 


CARBOHYDRATES 

WATEE 

ALBUMEN 

FAT 

ASH 

SUGAB 

STARCH 

Nestl6's,    .... 

6.15 

9.91 

4.46 

48.30 

35.00 

1.74 

Horlick's   .... 

5.08 

9.67 

.34 

66.39 

16.00 

2.02 

Neave's     .... 

4.27 

13.20 

1.70 

4.71 

74.14 

1.09 

In  discussing  the  popular  "  breakfast  foods  "  a  prominent 
writer  says :  — 

"  This  craving  for  something  new  to  stimulate  a  jaded  ap- 
petite, already  spoiled  by  endless  variety  and  bad  combi- 
nations, has  led  to  the  manufacture  of  a  cereal  preparation 
for  nearly  every  day  in  the  year.  No  better  comment  on  the 
laziness  or  willful  ignorance  of  the  American  providers  could 
be  made  than  this.  Little  do  the  people  know  about  wheat 
or  cooking  if  they  suppose  that  grain  can  be  changed  by 
manipulation  in  any  kind  of  machine  so  as  to  give  a  greater 
food  value  than  was  contained  in  the  grain.  While  it 
is  true  that  some  of  these  preparations  are  far  better  than 
the  half-cooked  grains  found  on  so  many  tables,  the  fact  re- 
mains that  it  is  the  cook  and  not  the  substance  which  is 
poor.  It  is  not  always  best  to  have  food  that  is  too  easily 
digested." 

"Apredigested  food  is  quickly  absorbed  into  the  circulation, 

1  "  Davis's  Chemistry  for  Schools,"  p.  285,  from  Kb'nig. 


182 


SANITARY   AND   APPLIED  CHEMISTRY 


and  hence  a  small  quantity  causes  a  sensation  of  fullness 
and  satisfaction,  which,  however,  soon  passes  away  and  faint- 
ness  results.  This  is  especially  true  of  the  sugars  and  the 
dextrins.  Frequent  meals  should  go  with  these  easily  ab- 
sorbed foods.  This  rapid  digestion  is  the  cause  of  much 
pernicious  eating  of  sweets  between  meals,  which  satisfies 
the  appetite  for  the  time  being  and  prevents  substantial 
quantities  of  other  foods  being  taken  at  the  time  when  they 
are  offered."  l 

It  is  well  to  note  that  the  oatmeal  sold  in  bulk  is  practi- 
cally the  same  as  that  sold  in  packages,  only  the  latter  has 
been  better  protected  from  vermin  and  dust.  It  is  true 
that  oatmeal  contains  more  protein  and  fat,  and  as  far  as 
the  analysis  shows,  offers  a  better-balanced  ration  than  most 
of  the  other  foods,  but  that  does  not  prove  that  it  should  be 
used  exclusively  as  a  breakfast  food.  The  cereals  —  wheat, 
barley,  corn,  and  oats  —  are  the  chief  source  for  the  manu- 
facture of  all  these  foods,  but  they  are  prepared  by  different 
processes. 

The  analysis  of  a  few  typical  brands  is  as  follows :  *  — 


s 

1 

a 

• 

*•  ~ 

^S 

B 

0  M 

§  s 

e 

(S 

S^rf 

§ 

b  P 

g  0 

<  ^ 

g 

5 

o 

c 

°£ 

B 

3 

llj 

Grape  Nuts 

8.00 

12.78 

78.78 

1.57 

2.02 

1.90 

$  .18 

MalU-Vlta      .        ... 

8.98 

11.84 

78.19 

1.55 

1.82 

2.67 

.11 

F.  8.  Rolled  A  vena    .    . 

9.68 

18.42 

60.85 

6.88 

2.22 

1.95 

.07} 

Ralston's  Health  Break- 

fast Food   

11.07 

12.55 

72.11 

1.72 

1.85 

1.20 

.07} 

Pillsbury's  VitOS    .     .     . 

11.19 

18.08 

78.44 

1.08 

.58 

.68 

.07 

Pettljohn'g  Breakfast  Food 

10.48 

12.11 

71.08 

2.50 

2.80 

1.58 

.07 

Quaker  Rolled  Oats    .    . 

9.40 

17.55 

61.56 

7.20 

2.40 

1.89 

.05 

Shredded  Whole  Wheat  . 

8.91 

11.82 

73.98 

0.87 

8.40 

1.57 

.11 

Vigor    

9.12 

14.46 

69.18 

1.65 

2.88 

8.21 

.15 

1  Richards  and  Woodman,  "  Air,  Water,  and  Food,"  p.  166. 
8  Slosson,  Wyoming  Exp.  Station,  Bui.  33. 


PREDIGESTED   AND   SPECIAL  FOODS  183 

From  a  study  of  the  analysis  of  a  large  number  of  these 
foods,  F.  W.  Robison l  arrives  at  these  conclusions  :  — 

"1.  The  breakfast  foods  are  legitimate  and  valuable 
foods. 

"2.  Predigestion  has  been  carried  on  in  the  majority  of 
them  to  a  limited  degree  only. 

"3.  The  price  for  which  they  are  sold  is,  as  a  rule, 
excessive  and  not  in  keeping  with  their  nutritive  values. 

"4.  They  contain,  as  a  rule,  considerable  fiber,  which, 
while  probably  rendering  them  less  digestible,  at  the  same 
time  may  render  them  more  wholesome  to  the  average 
person. 

"  5.  The  claims  made  for  many  of  them  are  not  warranted 
by  the  facts. 

"  6.  The  claim  that  they  are  far  more  nutritious  than  the 
wheat  and  grains  from  which  they  are  made  is  not  sub- 
stantiated. 

"7.  They  are  palatable,  as  a  rule,  and  pleasing  to  the 
eye. 

"8.  The  digestibility  of  these  products,  as  compared 
with  highly  milled  foods,  while  probably  favorable  to  the 
latter,  does  not  give  due  credit  to  the  former,  because  of 
the  healthful  influence  of  the  fiber  and  mineral  matter  in 
the  breakfast  foods. 

"  9.  Rolled  oats,  or  oatmeal,  as  a  source  of  protein  and  of 
fuel  is  ahead  of  the  wheat  preparations,  excepting,  of 
course,  the  special  gluten  foods,  which  are  manifestly  in  a 
different  class.  " 

Macaroni,  vermicelli,  and  spaghetti  are  made  in  Italy, 
France,  and  Switzerland,  from  certain  highly  nitrogenous 
varieties  of  wheat.  They  have  been  more  recently  made  in 
this  country.  The  macaroni  is  made  by  mixing  "  semolina  " 

1  Robison,  Michigan  Agric.  Exp.  Station,  Div.  Chem.,  1904. 


184 


SANITARY   AND  APPLIED   CHEMISTRY 


— the  hard,  flinty  part  of  the  wheat  grain  —  with  the  special 
wheat,  making  it  into  a  paste,  and  pressing  through  the 
bottom  of  a  cylinder  pierced  with  holes.  The  tubes  which 
come  through  the  perforations  are  cooled,  cut  in  lengths, 
and  dried  on  screens. 

The  composition  of  macaroni,  according  to  Church,1  is:  — 


FINE 
VABIKTT 

CHEAPER 
VARIETY 

Water     

130 

100 

Albuminoids,  &c  

11.1 

13.6 

Starch,  &c  

738 

708 

Fat     

.9 

23 

.4 

1.4 

Mineral  Matter     

.8 

20 

Macaroni  should  be  well  soaked  in  water  before  cooking, 
and  may  very  conveniently  be  served  with  cheese,  which 
adds  to  its  nutritive  value.  Sir  Henry  Thompson,*  in 
speaking  of  macaroni,  says  that  "  weight  for  weight  it  may 
be  regarded  as  not  less  valuable  for  flesh-making  purposes 
in  the  animal  economy  than  beef  or  mutton.  Most  people 
can  digest  it  more  easily  and  rapidly  than  meat.  It  offers, 
therefore,  an  admirable  substitute  for  meat,  particularly  for 
lunch  or  the  midday  meal." 

1  Church,  "Food,"  p.  81. 

8  Quoted  from  W.  G.  Thompson,  "Practical  Dietetics,"  p.  152. 


CHAPTER  XIV 
SUGARS 

History  and  Classification  of  Sugars.  Sugar  was  known 
at  such  an  early  age  that  the  date  of  its  discovery  is  lost. 
We  hear  of  its  use  in  India  perhaps  earlier  than  elsewhere. 
In  Europe  honey  was  used  for  sweetening  purposes  before 
sugar  came  into  general  use.  The  sugar  cane  was  culti- 
vated in  the  regions  adjoining  the  Mediterranean  Sea  as 
early  as  1148,  in  the  West  Indies  in  1506,  and  on  the  North 
American  continent  in  1800.  Sugar  was  first  noticed  as  a 
curiosity,  then  it  came  into  use  as  a  medicine,  and  finally 
has  become  a  necessary  part  of  our  diet.  Sugar  was  at  first 
confounded  with  manna,  and  was  supposed  to  be  the  dried 
juice  of  a  plant.  As  it  was  not  well  understood,  physicians 
regarded  it  as  having  an  injurious  effect  upon  the  system. 
Honey  was  thought  to  be  more  wholesome,  because  a 
"  natural  food."  We  find  the  price  of  sugar  quoted  at  45  cents 
per  Ib.  when  it  first  came  into  use.  The  amount  of  sugar 
used  in  civilized  countries  is  constantly  on  the  increase. 

The  sugars  have  essentially  the  same  food  value  as  the 
starches,  as  the  latter  must  be  converted  into  dextrin  or 
sugar  in  the  process  of  digestion.  As  cane  sugar  must  be 
changed  into  a  form  of  grape  sugar  before  being  digested, 
the  latter  is  often  spoken  of  as  a  "  predigested "  form  of 
food.  Although  sugar  is  an  excellent  energy  producer,  and 
in  fact  stands  at  the  head  of  the  list,  yet  an  overindulgence 
in  this  food,  especially  in  cane  sugar,  is  sure  to  cause 
flatulent  dyspepsia  and  other  disorders. 

185 


186  SANITARY   AND   APPLIED   CHEMISTRY 

About  8,000,000  tons  of  sugar  are  consumed  annually 
in  the  world,  and  English-speaking  nations  consume  the 
most  per  capita.  In  1895  the  per  capita  consumption  in 
England  was  86  Ib. ;  in  Germany,  France,  and  Holland, 
30  Ib. ;  in  Italy,  Greece,  and  Turkey  only  7  Ib. ;  and  in  the 
United  States,  66  Ib.1  The  per  capita  use  of  sugar  in  1903 
in  the  United  States  was  71.1  Ib. 

On  account  of  their  importance  as  food  materials  sugars 
should  be  thoroughly  discussed,  and  their  composition  and 
relations  to  other  nutrients  should  be  well  understood.  In 
general  the  sugars  are  recognized  by  the  fact  that  they  are 
readily  soluble  in  water ;  that  they  have  a  sweet  taste ;  and 
that  they  rotate  the  plane  of  polarized  light. 

There  are  a  large  number  of  sugars  known  to  the  chemist, 
but  up  to  the  present  time  the  property  of  sweetness  has  not 
been  identified  as  belonging  to  any  definite  molecule  or  to 
any  definite  combination.  In  addition  to  the  sugars,  there 
are  other  substances  that  are  sweet,  as,  for  instance,  the  alco- 
hols and  the  organic  compound  Saccharin,  C7H503SN,  which 
was  recently  discovered.  This  is  about  500  times  as  sweet 
as  cane  sugar.  The  addition  of  one  part  of  saccharin  to  1000 
parts  of  glucose  renders  the  latter  as  sweet  as  cane  sugar. 
Saccharin  is  sometimes  used  to  replace  sugar  for  diabetic 
patients,  but  it  has  no  food  value. 

The  sugars  that  are  in  common  use  may  be  divided  into 
two  general  classes:  the  sucrose,  or  cane  sugar,  group, 
having  the  composition  C^H^On,  and  the  glucoses,  or 
grape  sugars,  having  the  composition  C6H^06.  Sugars  of 
both  these  classes  are  found  under  various  names  in  a  large 
number  of  food  substances.  These  two  groups  are  also 
very  intimately  related,  so  that  by  "  inversion,"  with  heat 
and  dilute  acids,  some  of  the  members  of  the  first  group 
may  be  changed  to  those  of  the  second  group. 

1  Mary  Hinman  Abel.    (Thompson,  p.  128.) 


SUGAES  187 


SUCROSE, 

The  most  important  members  of  this  group  are  sucrose, 
maltose,  and  lactose.  Sucrose,  or  cane  sugar,  occurs  abun- 
dantly in  roots,  grasses,  and  stems  of  many  plants,  as  well 
as  in  fruits.  There  are,  however,  only  a  few  plants  from 
which  it  is  economical  to  make  sugar.  These  plants  are  the 
sugar  cane,  the  sugar  beet,  sorghum,  the  maple  and  birch 
trees,  cornstalks,  carrots,  and  sweet  potatoes.  About  two 
thirds  of  the  sugar,  as  estimated  by  Wiley,  is  made  from 
the  beet,  and  one  third  from  sugar  cane.  The  other  sources 
are  of  so  little  importance  that  they  need  only  be  mentioned 
incidentally.  Sugar  obtained  from  either  sugar  cane,  the 
beet,  or  any  other  of  the  sources  mentioned  has  the  same 
composition,  and  the  chemist  cannot  recognize  any  differ- 
ence between  the  products. 

From  13%  to  20%  of  sugar  is  found  in  the  stalks  of  sugar 
cane;  from  4%  to  15%  in  the  sugar  beet;  sometimes  as  much 
as  15%  in  sorghum;  and  the  sap  of  the  maple  tree  contains 
a  little  over  2  %  of  sugar. 

SUGAR  CANE 

Sugar  cane  belongs  to  the  family  of  grasses,  of  which 
there  are  many  varieties  growing  in  tropical  and  subtropical 
countries,  especially  in  the  moist  climate  of  islands  and  the 
sea  coast.  The  sugar  cane  is  successfully  cultivated  mainly 
in  Cuba,  the  West  Indies,  Louisiana,  the  Philippines, 
Java,  Brazil,  and  the  Hawaiian  Islands.  The  cane  nourishes 
best  where  the  mean  temperature  is  from  75°  to  77°  F.,  but 
it  grows  fairly  well  where  the  mean  temperature  is  not  be- 
low 66°  F.  Sugar  cane  is  propagated  not  by  seeds,  but  by 
cuttings.  The  young  cane  sprouts  from  the  roots  each  year, 
and  in  the  United  States  usually  three  crops  are  gathered 
from  one  setting,  so  on  each  plantation  one  third  of  the  space 


188  SANITARY   AND   APPLIED   CHEMISTRY 

is  set  with  new  cuttings  each  year.  In  the  West  Indies,  how- 
ever, the  sprouts  that  come  from  the  old  roots  are  cut  for  a 
series  of  years  till  at  last  the  plants  die,  and  are  then  replaced 
by  fresh  cuttings.  There  are  two  processes  of  extracting 
the  juice  from  the  sugar-bearing  material.  The  first  is  by 
crushing  in  roller  mills  and  the  second  is  by  diffusion.  The 
former  process  has  been  used  more  especially  for  making 
sugar  from  cane  and  the  latter  from  the  sugar  beet. 

MAKING  SUGAR  FROM  SUGAR  CANE 

The  average  analysis  of  the  ripe  cane  shows  it  to  contain 
of  sugar  18%,  fiber  9. 5%,  water  71%;  but  the  juice  contains 
of  sucrose  18%,  glucose  .30%,  gums  1.40%,  mineral  salts 
.30%,  water  80%.*  By  the  best  practice  about  84%  of  the 
juice  is  extracted. 

The  cane  is  cut  in  the  fall,  and  after  being  stripped  and 
topped  is  passed  through  a  "shredder,"  to  tear  it  to 
pieces,  then  several  times  between  heavy  horizontal  rollers, 
to  extract  the  juice.  The  "begasse"or  crushed  cane  left 
after  pressing  is  burned  as  fuel  under  the  boilers.  The  juice 
in  Louisiana  does  not  often  contain  over  14%  of  sucrose,  but 
in  Cuba  it  may  run  as  high  as  18%.  The  juice  is  passed 
through  a  screen  to  remove  suspended  matter,  then  nearly 
neutralized  with  milk  of  lime,  and  heated  to  coagulate  the 
albumen.  This  is  called  "  defecation."  The  lime  not  only 
neutralizes  the  acid,  which  is  quickly  formed,  and  thus  pre- 
vents it  from  "inverting"  the  sugar,  or  changing  it  to 
uncrystallizable  sugar,  but  it  unites  with  the  nitrogenous 
matter  and  causes  it  to  separate.  The  scum,  which  contains 
many  of  the  impurities,  is  allowed  to  rise  to  the  surface  and 
is  then  filtered  off  and  pressed  to  remove  as  much  of  the 
saccharine  liquid  as  possible.  The  pressed  filter  cake  may 

i  Thorp,  "  Outlines  of  Industrial  Chemistry,"  p.  388. 


SUGARS  189 

be  used  as  a  fertilizer.  The  juice  is  often  treated  with  sul- 
furous  acid,  which  is  made  by  burning  sulfur,  to  prevent 
fermentation  and  improve  the  color.  The  juice  must,  how- 
ever, be  left  slightly  alkaline  to  prevent  inversion.  The 
juice  may  also  be  filtered  through  bone  black  or  animal 
charcoal  in  order  to  remove  the  color,  but  this  is  not  often 
practiced  at  the  present  time  in  the  United  States. 

Formerly  the  saccharine  liquid  was  evaporated  in  open 
pans,  until  it  began  to  crystallize,  then  emptied  into  shallow 
tanks  and  stirred  till  it  was  cool.  The  mixture,  which  con- 
tained both  molasses  and  sugar,  was  placed  in  hogsheads 
having  holes  bored  in  the  end,  so  that  the  molasses  could 
drain  out.  By  this  process  a  sugar  called  "  muscovado  "  was 
produced,  which  contained  from  87  to  90%  of  sucrose.  The 
molasses  obtained  in  this  way  was  of  good  quality,  but  the 
process  was  not  economical,  as  so  much  of  the  sugar  was 
"  inverted  "  in  boiling. 

In  the  modern  sugarhouse  the  juice  is  first  concentrated 
in  "triple-effect"  evaporators,  which  utilize  the  steam  given 
off  from  one  pan  to  assist  in  heating  the  next,  and  are  there- 
fore very  economical ;  then  the  juice,  which  in  this  way  is 
much  concentrated,  is  run  into  the  vacuum  or  "  strike  "  pan. 
Usually  the  entire  system  of  evaporation  is  heated  by 
exhaust  steam,  and  this  conduces  greatly  to  the  economy  of 
the  process. 

In  the  vacuum  pan  the  juice  is  heated  by  steam  coils  and 
the  vapor  is  pumped  off,  thus  reducing  the  pressure  so  that 
the  sirup  will  boil  at  150°  to  180°  F.  instead  of  230°  to 
250°  F.,  which  would  be  the  case  in  the  open  pan.  After 
the  sugar  has  boiled  to  "  grain,"  or  till  it  begins  to  crys- 
tallize, some  more  sirup  is  admitted  to  the  pan  and  crystals 
of  sugar  are  gradually  "built  up"  till  a  sufficiently  large 
charge  is  obtained.  A  vacuum  is  maintained  on  the  pan 
during  the  entire  operation. 


190  SANITARY   AND   APPLIED   CHEMISTRY 

The  mixture  of  molasses  and  sugar  which  is  then  drawn  out 
of  the  vacuum  pan  is  called  masse  cuite.  A  part  of  it  is  run 
directly  into  the  "  centrifugals,"  and  the  rest  into  a  "  mixer," 
where  it  is  constantly  stirred  by  mechanical  means,  until 
there  is  an  opportunity  to  run  it  into  the  centrifugals.  The 
latter  revolve  on  a  perpendicular  axis  at  the  rate  of  about 
1200  times  per  minute.  The  outside  or  perpendicular  wall 
of  the  drum  is  perforated,  and  by  the  rapid  rotation  the 
sirup  "  flies  off "  into  the  space  outside  the  drum  and  runs 
into  a  receptacle  below.  The  top  of  the  drum  is  open  to 
facilitate  charging  and  washing,  and  the  charge  can  be 
dropped  out  at  the  bottom,  when  the  sirup  has  been  separated 
from  the  sugar.  The  sugar  while  in  the  centrifugal  may 
be  washed  by  throwing  into  it  while  running  a  small 
quantity  of  water  or  a  saturated  solution  of  pure  cane  sugar. 

The  liquid  that  has  run  through  the  centrifugal  together 
with  the  washing  is  diluted,  defecated,  and  again  boiled  down, 
forming  a  second  masse  cuite,  from  which  a  "  second  sugar  " 
is  obtained,  and  the  process  is  sometimes  repeated  to  obtain 
a  third  or  even  a  fourth  masse  cuite.  The  second  sugar  is 
often  mixed  with  the  concentrated  juice  before  it  is  run  into 
the  vacuum  pan,  to  save  time  in  "  building  up  "  the  grain  of 
the  sugar.  The  impure  molasses  finally  obtained  is  run 
into  a  cistern  and  worked  up  later  in  the  season  in  various 
ways.  Recently  it  has  been  found  to  be  economical  to  mix 
some  of  this  molasses  with  the  feed  of  the  mules  which  are 
employed  on  the  plantation. 

The  object  of  the  sugar  boiler  is  to  obtain  as  large  a  quan- 
tity of  cane  sugar,  and  as  little  uncrystallizable  or  "  invert " 
sugar  as  possible,  since  the  impure  molasses  is  of  little 
commercial  value. 

The  total  production  of  sugar  from  the  sugar  cane  in  the 
United  States  in  1905  was  766,680,000  Ib.1 

1  Ann.  Rep.  Dept.  Agric. 


SUGARS  191 

MAKING   SUGAR  FROM  THE   SUGAR  BEET 

It  was  in  1747  that  Marggraf,  a  German  chemist,  an- 
nounced that  it  was  possible  to  obtain  a  sugar  from  beet 
juice  which  was  identical  with  that  obtained  from  the 
sugar  cane.  Achard,  a  pupil  of  his,  actually  erected  a 
factory  and  made  some  beet  sugar,  but,  as  only  2  or  3%  of 
sugar  could  be  extracted  from  the  beets,  it  was  not  a  com- 
mercial success.  Napoleon  I,  in  1806,  caused  a  bounty  to 
be  offered  for  beet  sugar,  and  thus  the  manufacture  was 
greatly  stimulated.  At  first  the  beet  contained  only  6%  of 
sugar,  but  it  has  been  improved  so  much  by  cultivation  that 
it  now  often  contains  as  high  as  15%.  The  other  constituents 
of  beet  juice  embarrassed  the  sugar  boiler  greatly  for  some 
time,  but  the  process  of  manufacture  has  been  so  much  im- 
proved that  now  these  very  impurities  have  been  made  a 
source  of  profit. 

Although  several  methods  have  been  used  for  extracting 
sugar  from  the  beet,  the  "  diffusion "  process  has  been  the 
most  successful.  According  to  the  German  method,  the 
beets  are  cut  into  fine  chips,  and  are  then  put  into  a  series 
of  large  iron  vessels,  where  they  are  extracted  with  warm 
water.  The  "  battery  "  of  diffusors  is  so  arranged  that  the 
sweet  water,  heated  to  60°  C.,  may  be  circulated  from  one 
vessel  to  another,  till  the  sugar  is  practically  all  removed 
from  the  chips.  These  are  then  dropped  out  of  the  cylinder. 
It  is  again  filled  with  fresh  chips,  and  so  connected  as  to  be 
made  the  last  of  the  series  of  diffusors  through  which  the 
juice  is  circulating.  The  exhausted  chips  are  used  as  cattle 
food,  as  they  are  rich  in  nitrogenous  matter.  After  the 
water  has  remained  in  contact  with  one  lot  of  material  for 
20  minutes,  it  is  drawn  through  a  juice  warmer  before  it  is 
brought  into  the  next  diffusor.  Although  considerable  water 
is  used  in  this  process,  and  the  juice  must  be  concentrated 


192  SANITARY   AND   APPLIED   CHEMISTRY 

somewhat  more  than  when  extracted  by  crushing,  yet  the 
juice  is  so  much  more  free  from  foreign  nitrogenous  sub- 
stances that  the  diffusion  process  can  be  used  with  greater 
economy  and  success.  All  but  0.5%  of  the  sugar  is  ex- 
tracted.1 

The  crude  juice,  which  contains  about  as  much  sugar  as 
the  original  beet  juice,  is  heated  to  coagulate  the  albuminoids, 
and  then  lime  is  added  to  saturate  the  free  acids,  and  assist 
in  throwing  down  organic  matter.  Carbon  dioxid  gas  is  made 
to  pass  through  the  solution,  and  the  latter  is  then  forced 
through  the  filter  press.  Sometimes  this  operation  of  "  car- 
bonation"  is  repeated.  Then  the  juice  usually  goes  to  the  bone- 
black  niters.  Sometimes  the  treatment  with  lime  and  carbon 
dioxid  gas,  and  sulfurous  acids,  purifies  the  juice  so  that  no 
subsequent  treatment  with  bone  black  is  necessary.  Special 
care  and  treatment  is  required  to  make  from  the  sugar  beet  a 
fine  crystalline  sugar  which  has  no  unpleasant  taste  or  odor. 

The  molasses  obtained  by  this  process  is  boiled  down 
for  a  second  sugar  and  a  second  molasses.  As  the  latter 
contains  about  40%  of  sugar  that  cannot  be  crystallized,  this 
is  usually  recovered  by  treating  with  quicklime  to  form  a 
tricalcium  saccharate,  Cl2H.22On,  3  CaO.  This  latter  salt  is 
filter-pressed  to  separate  the  precipitate  from  the  sirup  and 
impurities,  and  this  precipitate  is  used  instead  of  lime  in  the 
defecation  of  fresh  juice,  or  it,  may  be  decomposed  by  passing 
carbon  dioxid  into  it.  In  1905,  635,526,080  lb.2  of  beet  sugar 
were  made  in  the  United  States. 

MAPLE  SUGAR 

The  manufacture  of  sugar  from  the  sap  of  the  hard 
maple,  Acer  saccharinum,  is  quite  common  in  the  extreme 
Northern  states  and  in  Canada.  The  sugar  season  is 
limited  to  6  or  8  weeks  in  the  spring.  The  sap  is  drawn 
from  the  trees  by  "tapping,"  or  making  an  incision 

i  Thorp,  "  Outlines  of  Industrial  Chemistry,"  p.  893. 
8  Ann.  Rep.  Dept.  Agric. 


SUGARS  193 

through  the  bark,  and  arranging  a  spout  to  carry  the  juice 
to  a  receptacle  below.  This  sap  is  then  concentrated  in 
shallow  pans  over  an  open  fire,  skimmed,  and  strained. 
Good  sirup  contains  about  62%  of  cane  sugar,  with 
varying  amounts  of  invert  sugar.  Maple  sugar  contains 
about  83%  of  cane  sugar. 

On  account  of  the  agreeable  taste,  which  is  due  to  certain 
characteristic  substances,  the  maple  products  always  com- 
mand a  high  price  in  the  market.  There  is  therefore  a 
temptation  to  imitate  these  products,  or  adulterate  them. 
Brown  sugar,  especially,  is  often  melted  with  inferior  maple 
sugar,  while  maple  sirup  is  adulterated  with  glucose,  molasses, 
or  refined  sugar.  Hickory  bark  is  said  to  be  used  as  a 
flavoring  material  in  the  imitation  maple  sugars.  It  is  not 
difficult  for  the  experienced  chemist  to  detect  the  spurious 
article.  In  1903,  5150  tons  of  maple  sugar  were  made  in 
the  United  States. 

The  manufacturers  of  adulterated  maple  sirups  go  so  far 
as  to  put  upon  the  package  a  guarantee  that  they  are  not 
adulterated,  and  do  not  contain  glucose,  corn  sirup,  or 
grape  sugar ;  but  they  omit  to  state  that  they  consist  wholly 
of  cane  sugar,  with  a  little  coloring  matter  and  flavoring 
material.  The  substances  used  may  not  be  injurious,  but 
there  is,  nevertheless,  a  fraud  upon  the  consumer  in  the 
price  he  is  charged  for  an  article  which  is  not  what  it 
purports  to  be  from  the  label. 

SORGHUM    SUGAR 

The  juice  of  the  sorghum  (Andropogon  sorghum  )  has  been 
used  for  a  long  time  in  the  United  States  by  the  farmers  as 
a  source  of  a  cheap  sirup,  and  the  United  States  Depart- 
ment of  Agriculture  at  one  time  carried  on  very  extensive 
experiments,  looking  to  the  possibility  of  making  a  crystal- 
lizable  sugar  from  sorghum.  The  cane  has  been  improved  so 


194  SANITARY   AND   APPLIED   CHEMISTRY 

that  it  often  contains  15%  of  sugar.  Many  of  the  difficul- 
ties have  been  overcome  by  the  use  of  the  "  diffusion  pro- 
cess" and  improved  methods  of  purification  of  the  juice. 
Although  a  good  quality  of  sugar  can  be  made,  yet  the 
manufacture  can  hardly  be  called  a  commercial  success,  and 
practically  no  sugar  is  made  from  sorghum.  Much  of  the 
so-called  sorghum  sirup  which  is  on  the  market  is  a  mix- 
ture of  sorghum  and  glucose. 

MOLASSES 

Molasses  is  of  various  grades,  and  contains  the  uncrys- 
tallizable  sugar,  some  cane  sugar,  gum,  coloring  matter, 
and  mineral  salts.  Where  the  drippings  from  the 
vessel  from  which  the  "first"  sugar  crystallizes  are 
used  as  molasses,  we  have  a  very  pure  product.  Since 
the  lower  grades  of  sugar  are  made  by  evaporation  of  the 
drippings  and  washings  of  the  several  crystallizations,  they 
contain  more  impurities  and  more  moisture  than  does 
granulated  sugar,  and  it  is  a  question  whether  they  are 
really  cheaper.  It  is  probably  on  account  of  its  ready 
solubility  in  the  mouth  that  we  get  the  impression  that  the 
impure  sugar  is  sweeter. 

SUGAR    REFINING 

Since  much  of  the  sugar  raised  on  the  plantations  is  put 
on  the  market  in  its  "raw"  condition,  it  must  be  refined  or 
purified  before  it  is  fit  for  use.  Sugar  refineries  are  usually 
situated  in  the  large  commercial  centers,  in  this  country 
at  New  York,  Philadelphia,  New  Orleans,  and  San  Francisco. 
The  buildings  are  very  high,  so  that  advantage  can  be  taken 
of  gravity  in  handling  the  product.  The  raw  sugar  is  par- 
tially dissolved  in  molasses  in  large  vats,  or  "melters," 
placed  below  the  floor  of  the  basement.  The  masse  cuite 
thus  formed  is  run  directly  into  the  centrifugals,  where  it  is 


SUGARS  195 

washed  slightly.  The  sugar  thus  obtained  is  "  melted "  in 
warm  water,  strained  from  the  coarser  particles  of  dirt,  and 
pumped  to  the  top  of  the  building. 

The  solution  may  be  "  defecated  "  by  boiling  with  lime, 
clay,  alum,  calcium  phosphates,  or  with  fresh  blood  from 
the  packing  house.  It  is  then  conveyed  to  "bag  filters," 
made  of  heavy  cotton  twill,  from  5  to  8  ft.  long.  Here 
the  refuse  that  would  not  settle  in  the  defecating  tanks 
is  collected.  The  liquor,  which  is  now  clear,  but  of  a 
brownish  color,  is  run  into  the  "  bone-black  filters."  These 
filters  are  long  cylinders,  often  extending  through  several 
stories,  fitted  with  a  perforated  bottom  over  which  a  blanket 
is  spread,  to  prevent  the  bone  black,  with  which  the  cylinder 
is  filled,  from  falling  through. 

The  sugar  solution  is  allowed  to  trickle  slowly  on  to  this 
filter,  and  to  remain  for  about  24  hours  in  contact  with  the 
bone  black ;  the  product  first  drawn  off  is  the  purest. 
When  the  bone  black  is  exhausted,  it  is  washed  with  water, 
which,  of  course,  is  saved,  and  the  bone  black  is  "  revivified  " 
by  being  burned  in  closed  retorts.  The  bone  black,  when  it 
is  cold,  is  sifted  and  the  dust  is  sold  for  the  manufacture  of 
fertilizers. 

The  colorless  liquor  is  then  ready  to  be  concentrated  in  the 
"vacuum  pan"  previously  described  (p.  184).  When  the 
masse  cuite  has  crystallized  sufficiently  to  make  "  loaf  sugar," 
it  is  run  into  conical  sheet-iron  molds  having  an  open- 
ing at  the  bottom,  and  the  sirup  runs  off.  Then  a  satu- 
rated solution  of  sugar  is  poured  on  the  top  of  the  "  sugar 
loaves  "  to  wash  out  the  uncrystallized  material.  This  pro- 
cess of  drainage  and  drying  may,  however,  be  much  short- 
ened by  placing  several  cones  at  a  time  in  a  centrifugal, 
and  "  throwing  out "  the  sirup  by  rapid  rotation. 

Experiment  97.  To  show  the  action  of  bone  black,  dissolve 
about  30  g.  of  brown  sugar  in  warm,  water,  add  at  least  25  g. 


196  SANITARY   AND  APPLIED   CHEMISTRY 

of  bone  black,  and  after  shaking  the  mixture  for  some  time, 
filter.  A  colorless  filtrate  should  be  obtained.  The  operation 
may  be  repeated  with  the  filtrate  if  it  is  not  colorless. 

GRANULATED    SUGAR 

To  make  granulated  sugar  directly,  the  mixture  of  sugar 
and  sirup,  frequently  3500  pounds  in  a  charge,  is  drawn 
off  from  the  vacuum  pan  into  a  mixer,  where  it  is  stirred 
while  cooling  to  prevent  the  grains  from  sticking  together. 
The  sugar  and  sirup  are  separated  in  the  centrifugal,  as  in  the 
case  of  making  raw  sugar,  and  the  sugar  is  washed  with  fresh 
water.  It  is  then  conveyed  to  the  "  granulator,"  which  is  a 
rotating  cylinder,  set  at  a  slight  incline,  and  heated  by  steam. 
Here  the  sugar,  which  enters  the  upper  end,  is  dried,  and  the 
grains  are  separated  one  from  another,  and  then  pass  through 
a  series  of  sieves,  and  are  finally  run  into  barrels  for  ship- 
ment. The  sirups  obtained  in  the  refining  process  maybe 
again  filtered  through  bone  black,  and  boiled  to  make  lower 
grades  of  sugar,  or  they  may  be  mixed  with  glucose  and  put 
on  the  market  directly  as  table  sirups. 

To  make  the  granulated  sugar  from  loaf  sugar,  the  cones 
are  crushed  and  sifted,  and  the  crystals  passed  over  a  heated 
table  into  the  packing  barrels.  Usually  a  little  "ultra- 
marine "  is  added  to  the  sugar  to  correct  the  slight  yellow 
color.  Although  this  coloring  matter  is  not  injurious,  yet 
in  some  manufacturing  processes  it  will  be  found  to  give  a 
disagreeable  odor  to  the  sirup,  on  account  of  the  decomposi- 
tion of  ultramarine  by  acids. 

Powdered  or  pulverized  sugars  are  made  from  the  same 
stock  as  the  granulated  sugar,  but  it  is  ground  and  bolted 
in  a  mill  similar  to  that  used  for  making  flour. 

Cut  sugar  is  made  from  the  sugar  loaves  by  sawing  them 
in  slices,  and  then  cutting  the  slices  into  rectangular  blocks 
by  the  use  of  a  gang  of  small  circular  saws. 


SUGARS  197 

On  account  of  the  cheapness  of  siigar,  there  is  little  danger 
of  adulteration,  but  lower  grades  are  more  readily  adulter- 
ated than  the  best  grade  of  granulated  sugar. 

PROPERTIES   OF   CANE   SUGAR 

Cold  water  dissolves  three  times  its  weight  of  cane  sugar. 

Rapid  boiling  changes  cane  sugar  to  barley  sugar,  a  trans- 
parent, noncrystalline  mass,  which  has,  however,  the  same 
chemical  composition  as  sugar. 

Experiment  98.  Melt  a  sample  of  cane  sugar  in  an  iron  pan 
or  spoon,  and  examine  the  product,  which  is  known  as 
"  barley  sugar." 

If  the  sample  is  heated  to  400°  !\,  a  substance  called  "  cara- 
mel "  results.  This  material  is  extensively  used  in  confec- 
tionery, and  is  a  harmless  coloring  matter  for  beer  and 
other  alcoholic  liquors. 

Experiment  99.  Heat  a  sample  of  sugar  to  a  higher  tem- 
perature than  in  Experiment  98,  and  dissolve  the  brownish 
substance  so  obtained  in  water.  Notice  the  taste  of  the 
solution.  When  cane  sugar  is  heated  with  an  acid  or  with 
many  salts  and  metals,  the  change  known  as  "  hydrolysis  " 
takes  place.  This  action  is  catalytic,  as  the  "  hydrolyte  "  does 
not  enter  into  chemical  combination  with  the  products  formed. 
This  hydrolysis  of  cane  sugar  to  an  invert  sugar  can  be 
expressed  by  the  equation:  C12H22011+H20=2  CeH^Og . 

Experiment  100.  To  50  cc.  of  a  fairly  strong  solution  of 
cane  sugar  add  5  cc.  of  hydrochloric  acid,  and  heat  the  so- 
lution gradually  to  70°  C.,  and  keep  it  at  this  temperature 
for  a  few  minutes.  By  this  treatment  the  sugar  is  "in- 
verted," and  the  presence  of  invert  sugar  may  be  determined 
by  the  Fehling's  test,  as  noted  in  Experiment  82. 

The  following  table 1  gives  the  average  composition  of  some 
common  grades  of  sugar :  — 

1  Thorp,  "  Outlines  of  Industrial  Chemistry,"  p.  400. 


198 


SANITARY   AND   APPLIED   CHEMISTRY 


RAW  SUGARS 

('ASK 
SUGAR 

GLUCOSE 

WATKR 

ORGANIC 
MATTER 

ASH 

Good  centrifugal    .     . 

96.0 

1.25 

1.00 

1.25 

.50 

Poor  centrifugal     .     . 

92.0 

2.60 

3.00 

1.75 

.75 

Good  muscovado    .     . 

91.0 

2.25 

6.00 

1.10 

.65 

Molasses  sugar        .     . 

88.0 

2.80 

3.00 

3.50 

2.70 

Manila  sugar          .    . 

87.0 

5.60 

4.00 

2.25 

1.25 

Beet  sugar,  1st       .     . 

95.0 



2.00 

1.75 

1.26 

REFINED  SUGARS 

Granulated  or  loaf  sugar 

99.8 

.20 







White  coffee  sugar  .     . 

91.0 

2.40 

6.50 

.80 

.30 

Yellow  sugar           .     . 

82.0 

7.60 

6.00 

2.60 

2.00 

Barrel  sirup             .     . 

40.0 

26.00 

20.00 

10.00 

6.00 

THE  FOOD   VALUE   OF   SUGAR 

The   food    value    of    sugar   has   been    summarized    as 
follows : l  — 

1.  When  the  organism   is   adapted  to  the  digestion   of 
starch  and  there  is  sufficient  time  for  its  utilization,  sugar 
has  no  advantage  over  starch  as  a  food  in  muscular  work 
except  as  a  preventive  of  fatigue. 

2.  In  small  quantities  and  in  not  too  concentrated  form, 
sugar  will  take  the  place,  practically  speaking,  weight  for 
weight,  of  starch  as  a  food  for  muscular  work,  barring  the 
difference  in  energy  and  in  time  required  to  digest  them, 
sugar  having  here  the  advantage. 

3.  It  furnishes  the  needed  carbohydrate  material  to  or- 
ganisms that  have  as  yet  little  or  no  power  to  digest  starch. 
Thus  milk  sugar  is  part  of  the  natural  food  of  the  infant 

4.  In  times  of   great    exertion  or  exhausting   labor,  the 
rapidity    with    which  it   is   assimilated   gives    it   certain 
advantages  over  starch. 

1  Mary  Hinman  Abel,  Farmer's  Bui.  93,  U.  S.  Dept.  Agric. 


SUGAKS  199 

MALTOSE 

Maltose  (C^H^On  +  H20) :  this,  together  with  dextrin, 
is  made  by  the  limited  action  of  dilute  acids  or  by  the  action 
of  malt  infusion  on  starch.  This  sugar  probably  does  not 
ferment  directly,  but  by  the  action  of  yeast  its  fermentation 
and  conversion  into  dextrose  go  on  simultaneously.  It  is  an 
ingredient  of  commercial  glucose,  and  is  also  the  sugar 
produced  by  the  action  of  the  ptyalin  of  the  saliva  on 
starch,  in  the  process  of  digestion. 

The  equation  for  changing  gelatinized  starch  to  maltose  is 
as  follows :  — 

CigHgoOis  +  H20  =  C6H100S  +  CuHzjOu. 

Starch  Dextrin  Maltose 

When  either  dextrin  or  maltose  is  heated  with  dilute  acid 
it  is  converted  into  dextrose.  The  hydrolysis  in  the  case  of 
maltose  would  be  represented  by  the  equation :  — 

C^I^Ou  -j-  H20  =  2  CgHjjOe. 

Maltose  Dextrose 


LACTOSE   (MILK   SUGAR) 


Lactose  (CuHjaOa+H^O)  is  made  commercially  by  treat- 
ing whey,  a  by-product  in  cheese  making,  with  chalk 
and  aluminum  hydroxid,  and  after  filtering  off  the  precipi- 
tate thus  produced,  the  filtrate  is  concentrated  in  a  vacuum 
pan,  and  when  sticks  or  strings  are  suspended  in  the  sirup, 
after  some  time  the  milk  sugar  crystallizes  on  them. 

This  sugar  is  not  as  sweet  as  cane  sugar,  but  it  is  very  useful 
in  "  modified  milk  "  in  making  dietetic  preparations,  and  as 
a  basis  for  the  pellets  used  by  homeopaths.  In  the  ordi- 
nary souring  of  milk  this  sugar  changes  to  lactic  acid.  On 
being  heated  with  dilute  acids  lactose  is  inverted,  forming 
dextrose  and  galactose  (see  reaction  under  sucrose). 


CHAPTER  XV 


IT  will  be  noticed  that  under  the  general  name  "  glucose  " 
there  are  grouped  a  number  of  substances  made  by  "  hydroly- 
sis "  from  starch,  such  as  dextrose,  and  also  substances 
such  as  levulose,  which  result  from  the  inversion  of  cane 
sugar. 

COMMERCIAL    GLUCOSE 

When  the  glucose  is  to  be  made  from  corn,  the  latter  is 
steeped  for  some  time  in  warm  water,  and  the  softened  grain 
is  crushed  in  a  "  cracker  "  to  loosen  the  germs.  The  coarse 
meal  passes  to  the  "separators,"  where  the  germs  being 
light  float  over  the  dam  at  the  end  of  the  tank.  These  germs 
are  often  used  for  making  corn  oil.  The  hulls  and  starchy 
matter  are  ground  fine,  and  passed  over  "  shakers "  to  re- 
move the  hulls.  The  starch  suspended  in  water  is  now 
ready  for  the  next  process. 

As  previously  stated,  when  starch  is  boiled  with  dilute 
acids  it  is  converted  into  a  mixture  of  compounds  of  the 
grape  sugar  group.  The  commercial  process  of  manufacture 
is  to  treat  the  starch  from  perhaps  1000  bu.  of  corn  suspended 
in  water  in  a  wooden  vat  of  3000  to  4000  gal.  capacity  with 
sulfuric  acid,  in  the  proportion  of  from  £  to  1£  Ib.  of 
sulf uric  acid  ( oil  of  vitriol )  to  100  Ib.  of  starch.  The 
liquid  is  boiled  by  means  of  a  steam  coil  with  free  or  con- 
fined steam  for  several  hours  or  till  a  sample  tested  with 
iodine  gives  no  blue  color.  Closed  "  converters "  are  also 
used  in  this  process  and  in  this  case  the  liquid  is  boiled 
under  pressure. 

When  the  process  of  conversion  has  been  carried  far 

200 


THE   GLUCOSE  OR   GRAPE  SUGAR   GROUP  201 

enough,  the  liquor  is  neutralized  with  marble  dust,  and  the 
calcium  sulfate  thus  formed  is  allowed  to  settle.  The 
solution  is  filtered  through  bag  filters  or  a  filter  press,  and 
is  then  run  through  bone-black  filters.  Concentration  in 
the  vacuum  pan  is  then  effected.  Some  rnanuf  acturers  filter 
several  times  through  bone  black,  and  some  use  sulfur  dioxid 
gas  to  bleach  the  product  and  arrest  fermentation. 

The  process  of  hydrolysis  would  in  part  be  represented  by 
the  equation  — 

(C6H1005)n  +  nH£  =  .(C.ftA). 
A  number  of  intermediate  products  are  formed. 

When  glucose  is  the  product  desired  the  conversion  of  the 
starch  is  arrested  while  there  is  still  considerable  of  the 
uncrystallizable  dextrin  in  the  product.  This  gives  a  heavy 
sirup.  If  the  conversion  is  more  complete,  and  the  concen- 
tration is  carried  farther,  the  product  is  a  solid  known  as 
"grape  sugar." 

In  addition  to  the  method  mentioned  for  making  glucose, 
another  process  has  recently  come  into  use  and  has  in  fact 
practically  superseded  the  former  process.  The  starch  is 
converted  to  glucose  by  adding  to  it  a  small  quantity  of 
hydrochloric  acid,  and  heating  for  some  time  under  con- 
siderable pressure.  The  excess  of  acid  is  afterwards  neutral- 
ized by  sodium  carbonate,  and  the  small  quantity  of  com- 
mon salt  left  in  the  product  is  said  to  improve  it  rather  than 
otherwise.  Some  sodium  sulfite  is  used  to  prevent,  as  far 
as  possible,  the  caramelization. 

The  composition  of  the  two  products  made  is  as  fol- 
lows : l  — 

GLUCOSE  (liquid)  GRAPE  SUGAR  (solid) 

Dextrose 34.3%  to  36.5%  72.0%  to  99.4% 

Maltose 4.6%  to  19.3%  0%to    1.8% 

Dextrin .   29.8%  to  45. 3%  0%to    9.1% 

Water 14.2%  to  17.2%  .6%  to  17.5% 

Ash .82%  to    .52%  .3%to    .75% 

1  Leach,  "  Food  Inspection  and  Analysis,"  p.  471. 


202  SANITARY   AND   APPLIED   CHEMISTRY 

Glucose  mixed  with  molasses  is  frequently  used  in  the 
manufacture  of  table  sirups ;  in  beer  to  take  the  place  of 
malt ;  in  the  manufacture  of  confectionery,  of  artificial  honey, 
and  of  maple  sirup,  jellies,  jams,  vinegar,  wine,  etc.  From 
some  experiments  made  by  the  author,  glucose  is  shown  to 
be  three  fifths  as  sweet  as  cane  sugar.1 

As  to  the  healthfulness  of  glucose,  the  committee  of  the 
National  Academy  of  Science,  to  whom  this  question  was 
referred  some  years  ago,  and  from  whose  report  many  of 
the  facts  are  gathered,  say  that  there  is  no  evidence  of  ill 
effects  from  its  use. 

The  report  concludes  thus:  "First,  the  manufacture  of 
sugar  from  starch  is  a  long-established  industry ;  scientific- 
ally valuable  and  commercially  important. 

"  Second,  the  processes  that  are  employed  at  the  present 
time  are  unobjectionable  in  their  character  and  leave  the 
product  uncontaminated. 

"  Third,  the  starch  sugar  thus  made  and  sent  into  com- 
merce is  of  exceptional  purity  and  uniformity  of  compo- 
sition, and  contains  no  injurious  substances. 

"Fourth,  having  at  best  only  two  thirds  the  sweeten- 
ing power  of  cane  sugar,  yet  starch  sugar  is  in  no  way  infe- 
rior to  cane  sugar  in  healthfulness,  there  being  no  evidence 
before  the  committee  that  maize  or  starch  sugar,  either  in 
normal  condition  or  fermented,  has  any  deleterious  effect 
upon  the  system  even  when  taken  in  large  quantities." 

The  glucoses,  maltose  and  milk  sugar,  reduce  Fehling's 
solution,  but  starch  paste  must  be  converted  by  acid,  and 
cane  sugar  must  be  inverted  before  testing. 

Experiment  101.  Use  a  thin  starch  paste  prepared  from 
some  of  the  starch  made  in  Experiment  72.  To  200  cc.  of 
this,  add  about  20  cc.  of  dilute  hydrochloric  acid,  and  boil  for 

1  Quarterly  Rep.  Kas.  State  Bd.  Agric.  1886,  p.  28. 


THE  GLUCOSE  OR  GRAPE  SUGAR  GROUP         203 

15  m.  Neutralize  the  solution  with  NaOH ;  cool  and  test  a 
portion,  1st,  with  iodin  for  starch ;  2d,  with  Fehling's  solu- 
tion for  dextrose.  There  may  be  some  dextrin  present,  in 
which  case  a  purple  color  will  be  obtained  by  iodin. 

Experiment  102.  Test  a  sample  of  commercial  "grape 
sugar "  for  starch  with  iodin,  and  for  a  reducing  sugar  by 
Fehling's  solution. 

Experiment  103.  Macerate  some  raisins  with  water,  filter 
the  solution,  and  test  a  portion  for  grape  sugar  or  invert 
sugar  by  Fehling's  solution. 

Experiment  104.  Crush  an  apple  and  squeeze  the  juice 
through  a  cloth,  filter  this,  and  test  for  the  invert  sugar. 
The  sugar  of  fruit  is  usually  invert  sugar,  and  this  like  dex- 
trose has  a  reducing  action  with  Fehling's  solution. 

Experiment  105.  Test  a  dilute  solution  of  pure  honey  for 
a  reducing  sugar  by  Fehling's  solution. 

Experiment  106.  As  sulfuric  or  sulfurous  acid  is  often 
used  in  the  manufacture  of  commercial  glucose,  it  is  some- 
times possible  to  detect  adulteration  of  honey  by  the  follow- 
ing test :  Add  to  a  dilute  solution  of  commercial  glucose  a 
drop  of  hydrochloric  acid  and  2  or  3  drops  of  a  solution 
of  barium  chlorid,  and  boil  the  solution.  The  formation  of 
a  white  precipitate  of  BaS04  shows  the  presence  of  sulfuric 
acid  or  a  sulfate. 

Experiment  106  a.  As  hydrochloric  acid  is  now  so  gen- 
erally employed  in  making  glucose,  test  a  dilute  solution  of 
glucose  for  a  chlorid  by  making  slightly  acid  with  nitric 
acid  and  adding  a  few  drops  of  silver  nitrate  (see  experi- 
ment 43). 

Experiment  107.  Eepeat  the  above  experiment,  using  a 
dilute  solution  of  honey. 


204  SANITARY   AND   APPLIED   CHEMISTRY 

Invert  sugar  is  of  importance,  since  it  results  from  the  in- 
version of  cane  sugar,  and  as  it  occurs  in  honey  and  many 
fruits.  It  is  a  mixture  of  equivalent  proportions  of  dex- 
trose and  levulose.  It  does  not  crystallize  readily,  and  is 
produced  in  the  boiling  of  acid  fruit  juices  with  cane  sugar, 
as  in  the  making  of  jellies,  etc.  Some  authorities  claim  that 
invert  sugar  is  sweeter  than  cane  sugar.  One  author,1  how- 
ever, reports  as  the  result  of  his  experiments  that  in  vert  sugar 
is  five  sixths  as  sweet  as  cane  sugar.  If  this  is  the  case,  we 
should  expect  that  more  sugar  would  be  required  to  sweeten 
canned  fruit  if  added  before  cooking  than  if  added  after- 
wards. Fruit  sugar,  or  levulose,  is  found  in  most  fruits,  and 
does  not  crystallize.  Invert  sugar  is  found  abundantly  in 
grapes,  forming  the  yellowish  white  granular  masses  in 
raisins.  Levulose  is  of  importance  as  a  food  for  diabetic 
patients,  as  they  utilize  it  more  easily  than  any  other  form 
of  carbohydrates. 

Experiment  108.  Test  some  dilute  cranberry  or  currant 
juice  with  Fehling's  solution  for  fruit  sugar,  then  boil  an 
equal  quantity  of  the  juice  for  15  m.  with  a  moderate 
amount  of  cane  sugar,  and  test  as  above.  Notice  by  the 
relative  quantities  of  the  precipitates  whether  the  fruit  acid 
has  "  inverted  "  some  of  the  cane  sugar. 

HONEY 

During  the  secretion  of  honey  in  the  body  of  the  bee,  su- 
crose, which  is  the  principal  constituent  of  the  nectar,  is 
mostly  changed  to  a  mixture  of  dextrose  and  levulose.  Wax, 
formic  acid,  and  flavoring  substances  from  the  flowers  are 
also  present.  It  has  been  estimated  that  to  obtain  a  kilo- 
gram of  honey  the  bee  must  visit  from  200,000  to  500,000 
flowers.  In  some  tropical  countries  certain  varieties  of 
flowers  furnish  a  honey  that  is  poisonous.  Genuine  honey 
1  Willard,  Trans.  Kan.  Acad.  Science,  Vol.  X,  p.  25. 


THE  GLUCOSE  OR  GRAPE  SUGAR  GROUP    205 

should  contain  not  more  than  8  %  of  sucrose,  not  less  than 
25  %  of  water,  not  less  than  0.25  %  of  ash,  and  from  60  to 
75%  of  reducing  sugar.  Whenever  the  dextrose  is  in  excess 
of  the  levulose,  it  indicates  adulteration  with  glucose.  If 
ash  is  high,  the  sample  is  regarded  with  suspicion.  Honey- 
comb consists  of  waxy  substances  which  are  probably  inca- 
pable of  digestion  but  not  necessarily  injurious. 

The  following  analysis  shows  the  average  composition  of 
genuine  honey : *  — 

Sucrose  (by  Clerget) 5%   to    7.64% 

Invert  sugar 66.37  %  to  78.80  % 

Water 12.00  %  to  33.00  % 

Ash 03%  to      .50% 

On  account  of  the  cost  of  honey  the  temptation  to  adul- 
teration is  very  great.  Cane  sugar  and  glucose  are  the  com- 
mon adulterants.  The  expedient  has  also  been  tried  of 
feeding  bees  upon  glucose,  but  it  is  said  that  they  do  not 
thrive  with  this  treatment.  It  is  a  common  practice  to  put 
up  the  so-called  "  strained  honey  "  in  jars,  with  a  piece  of 
the  comb  or  a  dead  bee,  as  evidence  of  its  genuineness. 
Artificial  combs  are  also  made,  but  have  not  found  much 
favor  with  bee  keepers.  Although  genuine  strained  honey 
may  be  found  upon  the  market,  we  usually  regard  all  honey 
sold  in  this  way  with  suspicion.  As  honey  is  actually  richer 
in  sugar  than  the  malt  extracts  recommended  for  invalids, 
and  as  this  sugar  is  nearly  all  in  a  form  to  be  readily  assimi- 
lated, it  is  considered  valuable  as  a  supplement  to  the  other 
carbohydrates  in  the  diet. 

Experiment  109.  If  honey  contains  dextrin,  this  is  a  good 
indication  of  adulteration  with  glucose.  To  test  for  dextrin 
add  to  the  suspected  sample  3  or  4  volumes  of  strong  alcohol. 

1  Canadian  Dept.  In.  Rev.,  Bui.  47. 


206  SANITARY   AND   APPLIED   CHEMISTRY 

In  the  presence  of  dextrin,  quite  a  precipitate  will  appear, 
but  in  genuine  honey  only  a  slight  cloudiness.1 

Experiment  110.  If  honey  contains  any  notable  quantity 
of  calcium  sulfate,  this  is  a  pretty  good  indication  of  its 
adulteration  with  glucose.  Test  some  diluted  honey  with 
ammonium  hydroxid  and  ammonium  oxalate  for  calcium. 

1  Leach,  loc.  cit.  p.  471. 


CHAPTER  XVI 
ROOTS,  LEAVES,  STALKS,  ETC.,  USED  AS  FOOD 

IN  addition  to  the  starch-bearing  vegetable  products  dis- 
cussed in  Chapter  XI,  there  are  a  number  of  roots  which  are 
not  particularly  valuable  as  sources  of  starch,  but  which 
give  a  variety  to  the  food  supply. 

The  carrot  belongs  to  the  botanical  order  Umbelliferse, 
which  includes  many  edible  plants  such  as  celery,  parsnip, 
and  parsley.  Wild  carrots  have  a  very  pungent  odor  and 
taste,  but  this  has  been  modified  by  cultivation  so  as  to  be 
mild  and  agreeable.  It  is  often  necessary,  however,  to  culti- 
vate a  taste  for  all  the  vegetables  of  this  class.  Carrots  con- 
tain no  true  starch,  but  about  2.5  %  of  pectose,  gum,  etc., 
4.5  %  of  sugar,  0.5  %  of  albuminoids,  and  89  %  of  water. 
When  carrots  are  boiled  they  lose  over  90  %  of  their  nutrient 
material.  This  fact  suggests  that  to  retain  any  food  value 
at  all,  carrots  should  be  cooked  in  a  soup  or  stew. 

Parsnips  have  also  been  cultivated  from  the  wild  parsnip, 
which  is,  like  the  carrot,  an  umbelliferous  plant.  The  pars- 
nip is  somewhat  more  valuable  as  food  than  the  carrot,  as 
the  former  contains  about  3.5  %  of  starch,  5  %  of  sugar, 
3.7  °J0  of  gum,  pectose,  etc.,  1.5  %  of  fat,  1.2%  of  albumi- 
noids, and  only  82  °/0  of  water.  It  loses  a  large  amount  of 
nutrient  material  in  boiling. 

Turnips  belong  to  the  order  of  Cruciferae.  They  contain 
pectose,  3  %,  instead  of  starch,  and  are  very  low  in  albumi- 
noids and  extractives.  Turnips  contain  92.8  %  of  water ; 
in  fact  they  contain  more  water  than  milk.  They  are  of 

207 


208  SANITARY   AND   APPLIED   CHEMISTRY 

little  value,  then,  except  for  their  flavor  and  to  furnish  variety 
to  the  bill  of  fare. 

Beets  are  a  more  important  food  than  any  of  those  just 
mentioned,  for  the  ordinary  garden  beet  has  been  cultivated 
so  that  it  contains  from  10  to  15  %  of  cane  sugar,  or  about 
as  much  as  the  variety  used  for  making  sugar.  Beets  also 
contain  2.4  %  of  pectose,  and  more  cellulose  than  the  other 
roots.  The  addition  of  vinegar  to  boiled  beets  helps  to 
soften  the  cellulose,  and,  it  is  said,  does  not  interfere  with 
the  digestion  of  other  carbohydrates.  After  beets  are  boiled 
they  contain  only  3  %  of  sugar. 

The  leaves  and  stalks  of  many  plants  are  valuable  both 
for  food  and  for  relishes.  One  reason  for  this  is  on  account 
of  the  large  amount  of  mineral  salts  that  they  contain. 
Some  of  these  would  be  tough  and  woody  if  grown  under 
the  ordinary  conditions,  but  if  they  are  grown  very  rapidly, 
in  an  exceedingly  rich  soil,  or  if  they  are  grown  partly 
underground,  or  in  the  shade,  they  are  quite  tender. 
Though  this  class  of  foods  often  contains  over  90%  of 
water,  yet  their  value  should  not  be  overlooked,  for  the  gluten 
and  starch  which  they  contain  are  often  in  such  a  condition 
that  they  can  be  readily  assimilated. 

Prominent  among  foods  of  this  class  should  be  men- 
tioned the  cabbage,  cauliflower,  and  kale.  The  cabbage 
contains  5.8%  of  carbohydrate,  1.8%  of  nitrogenous  matter, 
and  1.3%  of  mineral  matter,  but  when  cooked  the  per  cent 
of  water  is  increased  to  97.4%  and  the  other  constituents 
decrease  in  like  proportion.  In  general  it  may  be  said  that 
the  effect  of  cooking  is  to  greatly  diminish  the  amount  of 
nutrients  in  this  class  of  foods.  The  value  of  cabbage  as  a 
protection  against  scurvy,  for  those  who  are  for  a  long  time 
obliged  to  live  on  salted  or  canned  meats,  should  not  be  over- 
looked. 

Cabbage  is  sometimes  packed  in  salt  and  preserved  under 


ROOTS,  LEAVES,  STALKS,  ETC.,  USED  AS  FOOD   209 

the  name  of  "  sauerkraut."  Here  a  fermentation  takes  place 
and  various  organic  acids  are  formed. 

When  cooked  with  potatoes  to  furnish  the  starch,  and 
pork  to  furnish  fat  and  a  small  amount  of  proteids,  the 
deficiencies  of  cabbage  are  to  some  extent  made  up ;  really, 
however,  the  cabbage  is  but  a  flavoring  for  other  food  and 
adds  to  its  bulk. 

Many  other  succulent  vegetables  are  used  under  the 
common  name  of  "greens,"  and  each  has  its  agreeable 
flavor,  and  may  be  considered  of  value  rather  as  a  stimulant 
to  the  appetite  than  as  a  source  of  nutrient  material. 
Among  them  may  be  mentioned :  spinach,  dandelion,  endive, 
watercress,  beet  tops,  narrow-leaved  dock,  and  young  poke 
sprouts.  Lettuce,  which  also  belongs  to  this  class,  contains 
a  milky  juice,  having  mild  soporific  properties,  and  consid- 
erable mineral  salts  especially  potassium  nitrate.  Asparagus, 
which  is  in  much  more  common  use  than  most  of  the  foods 
mentioned,  in  the  wild  state  is  a  seashore  plant.  It  con- 
tains a  peculiar  crystallizable  principle  called  "  asparagin," 
C4H8N203,  which  has  diuretic  properties.  When  served 
with  toast,  the  combination  is  an  agreeable  and  useful  food. 
Celery  when  in  its  wild  state  was  known  as  "  smallage." 
By  intense  cultivation  much  of  the  disagreeable  odor  has 
been  removed,  and  it  has  found  great  favor.  On  the  con- 
tinent of  Europe  the  root  is  boiled,  but  in  the  United  States 
the  stalks,  which  are  grown  so  that  they  are  protected  from 
too  much  light,  are  eaten  raw  for  their  agreeable  flavor. 

Rhubarb  (Rheum  raphonticum),  under  the  name  of 
"pie  plant,"  is  a  useful  garden  production.  The  leaf 
stalks  when  cooked  with  sugar  are  used,  on  account  of  their 
flavor  and  the  acid  which  they  contain.  As  the  plant  is  a 
slight  laxative  it  may  be  useful  in  cases  of  constipation. 
Rhubarb  contains  a  peculiar  flavoring  substance  and  con- 
siderable acid  potassium  oxalate. 


210  SANITARY   AND  APPLIED   CHEMISTRY 

Experiment  111.  Express  the  juice  from  several  stalks 
of  rhubarb  and  filter  it.  Add  to  some  of  the  clear  juice 
a  little  of  a  solution  of  calcium  chlorid,  and  notice  the 
precipitate  of  calcium  oxalate  produced. 

The  onion,  leek,  and  garlic  are  chiefly  prized  for  their 
pungent  volatile  oil,  rich  in  sulphur,  which  makes  them 
useful  in  flavoring  other  food. 

The  tomato,  although  not  properly  belonging  to  this 
class,  may  be  here  discussed.  It  is  a  native  of  South 
America,  and  was  introduced  into  Europe  in  1596.  It 
has  been  grown  and  used  in  enormous  quantities  in  the 
United  States  since  about  1850.  The  raw  tomato  con- 
tains 91.9  %  of  water,  1.3%  of  nitrogenous  matter,  5  % 
of  carbohydrates  and  .7%  of  mineral  matter,  and  there- 
fore is  not  very  valuable  as  a  nutrient,  but  is  properly 
classed  as  a  relish. 

Tomatoes  probably  owe  their  acidity  to  the  presence  of 
malic  acid.  When  made  into  "catsup,"  the  product 
is  often  grossly  adulterated  and  colored  with  aniline  col- 
ors, and  various  preservatives  are  also  used. 

ALQJE,   LICHENS,   AND   FUNGI   USED  AS  FOOD 

The  most  important  of  the  algae  is  the  Irish  or  Car- 
rageen moss.  When  dried,  as  usually  prepared  for  market, 
it  contains  9.4%  of  nitrogenous  matter  and  55.4%  of  a 
vegetable  mucilage.  Its  value  as  a  nutrient  is  not  fully 
understood. 

Iceland  moss  is  darker  in  color  than  Irish  moss  and  con- 
tains 8.7%  of  proteids  and  70%  of  a  lichen  starch,  which  is 
unaffected  by  digestion,  and  probably  does  not  form  glyco- 
gen.  It  has  not  been  proved  that  it  has  any  value  as  food. 

The  edible  fungi  are  popularly  classed  as  mushrooms  and 
the  poisonous  ones  as  toadstools,  but  this  is  not  a  scientific 
classification.  Mushrooms  are  employed  not  only  for  flavor- 


ROOTS,  LEAVES,  STALKS,  ETC.,  USED  AS  FOOD   211 

ing,  but  also  as  food.  They  are  grown  in  large  quantities  in 
Europe  in  caves  and  cellars,  in  an  exceedingly  rich  soil.  They 
contain  from  1.19  to  6.1  %  of  proteids,  and  from  1.2  to  6  %  of 
carbohydrates,  but  starch  is  not  present  among  the  carbohy- 
drates. Although  the  analysis  shows  considerable  nitrogen, 
much  of  this  is  in  such  a  combination  that  it  is  not  available 
for  nutrition.  It  is  said  that  mushrooms  are  not  easily  di- 
gested, on  account  of  the  large  amount  of  cellulose  which 
they  contain.  Some  authorities  claim  that  their  use  as  a 
nutritious  food  should  be  encouraged,  while  others  believe 
them  to  be  simply  a  rather  expensive  flavoring  material. 
The  varieties  known  as  truffles  and  morels  are  quite  popular 
in  England  and  on  the  Continent. 

Unfortunately  several  varieties  of  mushrooms  are  ex- 
tremely poisonous.  In  some  cases  the  symptoms  of  the 
poisoning  do  not  appear  till  after  more  than  twenty-four 
hours.  The  poisonous  substance  is  an  alkaloid,  a  glucoside, 
or  a  toxalbumin,  and  is  of  different  composition  in  the  dif- 
ferent varieties.1  As  the  taste  for  mushrooms  is  being  cul- 
tivated, a  larger  number  of  persons  are  becoming  acquainted 
with  the  characteristics  of  edible  mushrooms,  and  in  some 
countries  special  pains  is  taken  to  educate  the  common 
people  to  recognize  the  nonpoisonous  varieties.  There  seems 
to  be  no  safe  rule,  however,  by  which  we  can  distinguish 
between  the  poisonous  and  edible  varieties,  and  it  is  hazard- 
ous for  persons  not  well  acquainted  with  fungi  to  attempt  to 
do  this. 
1  See  U.  S.  Dept.  Agric.,  Div.  Microscopy,  Food  Products,  1893-1894. 


CHAPTER   XVII 
THE  COMPOSITION  AND  FOOD  VALUE  OP  FRUITS 

THE  term  "fruit,"  in  the  restricted  sense,  includes  the  pulpy 
substance  inclosing  the  seeds  of  various  plants,  and  especially 
those  which  are  edible  in  the  raw  state. 

Fruits  are  essential  to  the  distribution  of  plants,  and 
have  been  utilized  by  man  as  food,  as  an  agreeable  luxury, 
and  an  aid  to  digestion.  In  general  it  may  be  stated  that 
the  seed  is  surrounded  by  some  sweet,  or  edible  envelope, 
to  attract  birds,  insects,  and  quadrupeds,  and  in  this  way 
insure  the  scattering  of  the  seed  over  a  wider  extent  of 
territory. 

The  seed  proper  is  surrounded  by  a  fleshy  portion  known 
as  the  pericarp.  A  green  fruit  does  not  differ  very  much 
from  the  leaf  in  composition,  but  in  the  process  of  ripen- 
ing, under  the  influence  of  sunlight,  the  fruit  undergoes 
a  remarkable  change  in  color,  texture,  composition,  and 
flavor.  During  the  change  it  ceases  to  act  on  air  like  a 
leaf,  but  begins  to  absorb  oxygen,  and  give  out  carbon  dioxid 
gas. 

As  the  process  of  ripening  goes  on,  both  the  invert  sugar 
and  the  sucrose  increase  and  the  starch  and  free  acid  de- 
crease. After  the  disappearance  of  the  starch  the  sucrose 
disappears  quite  rapidly  on  account  of  its  change  to  invert 
sugar.  Malic  acid  appears  to  decrease,  but  this  phenomenon 
is  largely  due  to  the  fact  that  it  is  formed  in  the  early  life 
history  of  the  fruit,  and  is  diluted  by  its  growth.  These 
changes  are  very  well  illustrated  by  the  examination  of  the 

212 


analyses  of  Ben  Davis  apples,  which  were  made  at  different 
stages  of  their  growth.1 


DATE  OF  ANALYSES 

TOTAL 
SOLIDS 

ACID  AS 
MALIC 

STABOH 

SUCBOSE 

INVEBT 
SUGAB 

June  16  

13.63 

1.64 

2.23 

0.49 

2.35 

June  30        

13.37 

1.27 

3.03 

.67 

3.04 

July  13 

13  58 

3  72 

1.21 

5.09 

July  28    

15.71 

.89 

3.67 

1.13 

4.52 

Aug.  18  

14.92 

.78 

3.16 

1.46 

4.36 

Sept.  24  

15.05 

.52 

2.40 

2.59 

4.83 

Oct.  16    

14.86 

.52 

1.46 

3.13 

5.30 

Oct.  28    

14.82 

.94 

3.92 

5.53 

Oct.  30    

14.68 

.43 

.38 

3.87 

6.84 

Nov.  5     

15.73 

.41 

3.71 

6.83 

It  is  supposed,  while  ripening,  that  the  insoluble  pectose 
changes  into  pectin  and  secondary  substances  of  a  gelatinous 
nature.  The  tannin  that  made  the  fruit  astringent  also  dis- 
appears. As  the  fruit  becomes  over-ripe,  some  of  the  sugar 
and  acid  is  oxidized,  or  otherwise  changed,  and  the  fruit 
loses  its  agreeable  flavor.  On  cold  storage  this  latter  change 
is  deferred  by  the  low  temperature,  but  a  very  short  exposure 
to  air,  at  ordinary  temperature,  causes  the  fruit  not  only  to 
appear  over-ripe,  but  to  decay  quickly.  During  the  process  of 
decay,  which  is  assisted  by  fermentation,  carbon  dioxid  and 
alcohol  are  at  first  formed  from  the  sugar,  and  later  the 
alcohol  is  oxidized  to  acetic  acid,  and  finally  in  the  decayed 
fruit  the  seed  is  set  free,  ready  to  start  a  new  plant. 

Eruits  owe  their  agreeable  taste  to  the  right  proportion 
of  the  constituents  mentioned  in  the  table  on  p.  214,  and  to 
the  compound  ethers  and  essential  oils  that  may  be  present. 

1  Bigelow,  Gore,  and  Howard,  U.  S.  Dept.  Agric.,  Bu.  Chem.,  Bui. 
94,  p.  46. 


214 


SANITARY  AND   APPLIED   CHEMISTRY 


These  flavoring  substances  are  many  of  them  present  in  such 
small  quantity  that  they  are  not  mentioned  in  the  analysis. 

The  composition  of  some  of  the  most  important  fruits,  as 
purchased,  and  including  the  refuse,  is  given  by  Atwater 
and  Bryant,1  as  follows :  — 

FRUITS 


REFUSE 

WATER 

PEOTEIN 

5 

h 

TOTAL  CAR- 
BOHYDRATE 

CRUDE  FIBER 

3 
o 

Apples  

26.0 

68.8 

.3 

.3 

10.8 

.8 

Blackberries  .... 

86.3 
76.8 

1.8 
.9 

1.0 

.8 

10.9 
15.9 

2.5 

.6 
.6 

Cranberries    .... 



8S.9 
85.0 

.4 
1  5 

.6 

9.9 
12  8 

1.5 

.2 

.7 

Pigs,  fresh  

79.1 

1.5 

18.8 

.6 

250 

58.0 

1  0 

1.2 

14.4 

.4 

Musknielon     .... 
Oranges     

50.0 
27.0 

44.8 
27.0 

.3 
.6 

.1 

4.6 

8.5 



.8 
.4 

Pears          .     . 

100 

76.0 

5 

4 

12.7 

.4 

Plums    

50.0 

74.6 

.9 

19.1 

.5 

Raspberries    .... 
Strawberries  .... 
Watermelon*.    .    .    . 

22. 
59.4 

85.8 
85.9 
92.4 

1.0 
.9 
.4 

.6 
.2 

12.6 
7.0 
6.7 

2.9 

.6 
.6 
.8 

Some  fruits  that  seem  to  "  melt  in  the  mouth  "  really  do 
contain  considerable  soluble  matter.  It  is  a  well-known 
fact  that  sugar  disguises  acids,  and  that  an  agreeable  taste 
in  preserved  fruits  is  often  due  to  a  judicious  mixture  of 
the  acid  and  the  sweet.  The  most  important  nutritive 
material  in  fruits  is  in  the  carbohydrate  group :  of  course 
there  are  some  special  fruits  like  the  olive  and  the  avocadro 
which  contain  large  quantities  of  fats.  Although  starch  is 
found  at  certain  stages  of  growth,  sugar  is  the  most  abundant 

1  U.  S.  Dept.  Agric.,  Office  of  Exp.  Sta.,  Bui.  28.         2  Edible  portion. 


COMPOSITION   AND   FOOD   VALUE  OF   FRUITS      215 

of  the  carbohydrates.  This  is  usually  invert  sugar,  but  apri- 
cots, pineapples,  and  apples  contain  also  cane  sugar.  This 
fact  has  an  important  bearing  on  the  dietetic  use  of  fruits, 
as  invert  sugar  is,  in  some  diseases,  as  diabetes,  more  easily 
assimilated  than  cane  sugar. 

The  pectous  bodies  referred  to  above  are  not  very  well 
understood,  but  are  supposed  to  be  related  to  the  carbohy- 
drates. The  insoluble  galacto-araban  is  supposed  to  give 
the  property  of  hardness  to  unripe  fruits  and  vegetables,  and 
is  the  basis  for  the  making  of  jelly.  The  statement  has  been 
made  that  as  the  fruit  becomes  riper  the  pectose  is  changed 
by  the  action  of  acids  into  pectin,  a  vegetable  jelly,  which 
causes  the  juice  after  boiling  to  gelatinize  when  cooled.  This 
may  be  noticed  in  the  juice  that  exudes  in  the  baking  of  apples. 
It  is  supposed  that  by  too  long  boiling  these  pectous  com- 
pounds are  concentrated  into  a  more  soluble  modification,  and, 
if  this  is  true,  it  may  explain  the  fact  that  sometimes  fruit 
juices  that  have  been  boiled  for  a  long  time  become  thick 
and  viscid,  but  do  not  form  a  true  jelly.  A  partially  ripe 
fruit  is  better  adapted  to  making  a  jelly  than  one  that  is 
fully  ripe. 

From  what  has  been  said  it  is  evident  that  pectin  bodies 
are  substances  of  undetermined  function  very  widely  dis- 
tributed in  plant  tissues.  They  occur  both  in  soluble  and 
insoluble  forms. 

In  the  study  of  these  bodies  "  the  most  important  problem 
appears  to  be  the  quantitative  determination  of  the  pectin 
bodies  occurring  in  a  given  tissue,  because  such  a  method 
could  be  used  to  determine  the  function  of  the  material  in 
plants :  whether,  for  example,  it  is  a  reserve  material,  a  by- 
product, is  used  for  structural  purposes,  or  has  all  three 
functions  or  two  of  them ;  whether  the  nature  of  the  pectin 
body  changes  with  the  growth  of  the  tissue,  or  possesses  a 
practically  constant  composition ;  whether  the  pectin  bodies 


216  SANITARY  AND   APPLIED   CHEMISTRY 

obtained  from  different  sources  are  identical,  are  mixtures 
of  the  same  substances  (such  as  araban  and  galactan)  in 
varying  proportions,  or  are  inherently  different. " 1 

Experiment  112.  To  the  filtered  juice  of  a  ripe  apple  add 
an  equal  bulk  of  alcohol,  and  a  gelatinous  mass  consisting 
largely  of  pectin  will  be  precipitated.  This  may  be  dried, 
and  it  will  be  found  that  the  powder  thus  obtained  is  solu- 
ble in  cold  water. 

Experiment  113.  Stew  a  handful  of  cranberries,  filter  the 
juice,  and  allow  it  to  stand  till  cold,  when  an  abundant  jelly 
is  obtained. 

Experiment  114.  Test  some  green  fruit,  a  persimmon 
or  banana,  for  tannin  by  extracting  the  juice,  filtering,  and 
adding  a  small  quantity  of  ferric  chlorid.  The  production 
of  a  black,  or  greenish-black,  color  indicates  tannin. 

The  acidity  of  fruits  is  due  to  the  presence  of  the  free 
acids,  malic,  citric,  tartaric,  or  racemic,  or  their  acid  salts. 
They  not  only  have  an  agreeable  acid  taste,  and  they  serve 
as  appetizers,  but  when  oxidized  in  the  body  are  converted 
into  the  corresponding  carbonates,  and  these  help  to  render 
the  blood  more  alkaline  and  the  urine  less  acid. 

Malic  acid  (H2C4H4Oj)  is  found  in  many  acid  fruits,  as 
cherries,  apples,  raspberries,  gooseberries,  rhubarb,  unripe 
mountain  ash  berries,  etc. 

Experiment  115.  Add  to  a  solution  of  malic  acid,  calcium 
chlorid,  ammonium  chlorid,  and  ammonium  hydroxid  in 
excess.  There  should  be  no  precipitate,  but  upon  adding 
to  this  3  volumes  of  alcohol,  calcium  malate  (CaC4H404, 
3  H80)  should  separate  out  as  a  precipitate. 

1  BIgelow,  Gore,  and  Howard,  U.  S.  Dept.  Agrlc.,  Bu.  Chem.,  Bui. 
94,  p.  86. 


COMPOSITION   AND   FOOD   VALUE   OF  FRUITS      217 

Experiment  116.  Since  the  acid  potassium  malate  exists 
in  the  stalks  of  the  common  rhubarb,  the  juice  that  is  ex- 
pressed from  this  may  be  filtered  and  tested  for  malic  acid 
by  the  test  described  in  Experiment  115. 

Citric  acid,  H3C6H607,  occurs  in  the  juice  of  lemons,  cur- 
rants, unripe  tomatoes,  gooseberries,  etc.  It  is  made  on  a 
large  scale  from  lime  or  lemon  juice,  by  saturating  the  juice 
with  chalk;  the  precipitate  of  calcium  citrate  is  decom- 
posed by  an  equivalent  quantity  of  sulfuric  acid  and  filtered 
from  the  calcium  sulf ate.  Evaporate  the  filtrate  and  crystal- 
lize out  most  of  the  calcium  sulfate,  and  from  the  mother 
liquor  allow  the  citric  acid  to  crystallize. 

Experiment  117.  Make  citric  acid  from  the  juice  of  at 
least  two  lemons,  as  above  described. 

Experiment  118.  Add  a  moderate  quantity  of  calcium 
chlorid  to  a  concentrated  solution  of  citric  acid,  and  then 
add  sodium  hydroxid  till  the  solution  is  nearly  neutral. 
Calcium  citrate,  Ca3(C6H507)2,  will  be  formed. 

Experiment  119.  Try  the  above  test  with  a  concentrated 
and  filtered  sample  of  lemon  juice,  and  note  the  formation 
of  the  precipitate  of  calcium  citrate. 

Tartaric  acid  (H2C4H406)  is  found  in  many  fruits,  particu- 
larly ripe  grapes,  as  acid  potassium  tartrate  (KHC4H406). 
When  the  "  must "  ferments  the  "  cream  of  tartar  "  precipi- 
tates as  the  alcohol  increases,  and  this  precipitate  is  known 
in  the  market  by  the  name  of  "  argol,"  or  crude  tartar.  It 
is  frequently  much  contaminated  with  calcium  sulfate, 
which  is  used  in  "  plastering  "  the  wine.  To  make  tartaric 
acid  from  this,  the  solution  of  the  argols  is  treated  with 
milk  of  lime  to  form  the  calcium  tartrate,  and  the  latter  salt 
is  suspended  in  water  and  treated  with  an  equivalent  of  sul- 
furio  acid,  and  the  calcium  sulfate  so  formed  is  filtered  off, 


218  SANITARY   AND   APPLIED   CHEMISTRY 

and  the  tartaric  acid  is  obtained  in  crystals  by  concentration 
of  the  filtrate. 

Experiment  120.  Add  to  a  concentrated  solution  of  tar- 
taric acid  a  concentrated  solution  of  potassium  chlorid,  when 
a  precipitate  of  acid  potassium  tartrate  will  be  formed  on 
shaking  and  allowing  to  stand  at  ordinary  temperature. 
The  test  is  more  delicate  if  the  solution  is  nearly  neutral- 
ized with  sodium  carbonate  before  the  potassium  chlorid  is 
added. 

Experiment  121.  Make  a  similar  experiment  with  filtered 
grape  juice,  which  may  conveniently  be  obtained  from 
canned  grapes.  A  more  delicate  test  is  made  by  adding  to 
100  cc.  of  the  fruit  juice  a  few  drops  of  strong  acetic  acid,  a 
few  drops  of  a  concentrated  potassium  acetate  solution,  and 
15  g.  of  pure,  finely  ground  potassium  chlorid ;  dissolve  the 
latter  salt  by  shaking  and  add  20%  of  95%  alcohol.  Stir 
and  shake  vigorously  to  assist  in  the  crystallization  of  the 
acid  potassium  tartrate. 

Cultivation  has  changed  the  character  of  many  fruits, 
and  has  much  improved  their  flavor,  so  that  many  luscious 
fruits  have  been  developed  from  disagreeable,  or,  to  say  the 
least,  very  medium  stock.  Cooking  improves  many  fruits 
by  softening  the  cellulose  and  converting  the  gums  and  al- 
lied bodies  into  a  gelatinous  form.  Sucrose  is  inverted 
and  pectin  bodies  converted  into  soluble  forms.  If  there  is 
starch  remaining,  this  is  made  more  digestible  by  cooking. 
There  are  many  fruits  that  in  the  raw  state  are  not  suitable 
to  use  as  food  for  persons  with  dyspeptic  tendencies.  They 
are,  however,  very  satisfactory  and  useful  when  suitably 
cooked.  Apples,  pears,  quinces,  and  cranberries  belong  to 
this  class.  It  should  also  be  noted  that  a  jelly  made  from 
a  fruit  juice  is  usually  much  more  acceptable  to  an  invalid 
and  less  irritating  in  its  action  than  the  raw  fruit  or  the 


219 

jam.  This  is  especially  true  of  raspberries,  blackberries,  and 
currants,  on  account  of  the  numerous  fine  seeds  that  are 
present  in  the  jam. 

JAMS    AND    JELLIES    AND    THEIR    ADULTERATION 

Although  a  few  years  ago  preserved  fruit  products  were 
all  prepared  by  the  housewife,  at  the  present  time  much  of 
this  work  is  turned  over  to  the  manufacturer,  and  he  has 
the  opportunity  and  often  the  incentive  to  falsify  the  mate- 
rial, and  to  give  it  a  fictitious  value  in  color,  odor,  sweetness, 
flavor,  and  preservative  qualities.  Much  work  has  been  done 
on  this  subject  by  the  United  States  Department  of  Agri- 
culture and  at  State  Experiment  Stations.  The  presence  in 
these  products  of  anything  in  addition  to  the  fruit  and  cane 
sugar  should  be  regarded  as  an  adulteration.  If  they  are  made 
up  with  foreign  materials  they  should,  in  the  interest  of 
the  purchaser,  at  least  be  labeled  "compound." 

The  substitute  for  jam  and  jelly,  which  is  sold  at  say 
10^  per  half-pound  jar,  is  often  made  of  apple  juice  or  refuse 
from  canning  factories,  and  glucose,  or  starch,  colored  with 
coal-tar  dyes  to  imitate  any  natural  product,  as  straw- 
berry, currant,  etc.,  and  occasionally  flavored  with  an 
artificial  fruit  essence.  Sometimes  a  little  "  saccharin  "  is 
added  to  give  a  sweeter  taste  than  the  glucose  would  im- 
part, and  usually  some  preservative,  as  salicylic  acid,  sodium 
benzoate,  or  sulfite  is  used. 

As  it  is  difficult  to  secure  sufficient  stiffness  in  an  apple- 
jelly  stock  with  glucose,  a  little  alum  and  sulfuric  acid  or  some 
tartaric  or  phosphoric  acid  is  added  to  cause  the  mass  to 
gelatinize.1  In  the  cheapest  jellies,  since  there  is  very  little 
pectin  or  malic  acid,  starch,  and  agar-agar  are  sometimes 
added  to  cause  the  mass  to  thicken  sufficiently. 

Foreign  seeds,  like  that  of  the  clover,  are  sometimes  used. 
1  Leach,  "  Food  Inspection  and  Analysis,"  p.  716. 


220  SANITARY  AND   APPLIED  CHEMISTRY 

Although  a  sample  of  jam  may  contain  the  seeds  of  the 
genuine  fruit,  and  so  appear  to  be  genuine,  yet  the  fruit  may 
be  first  used  to  make  a  high  grade  of  jelly,  and  the  residue 
may  be  afterwards  worked  up  into  a  cheap  jam. 

Experiment  122.  The  test  for  a  coal  tar  dye  in  jelly 
may  be  made  as  follows :  Strips  of  a  fine  woolen  cloth,  such 
as  "  nun's  veiling,"  are  boiled  with  a  solution  of  soap,  and 
then  thoroughly  washed.  One  of  these  strips  is  then  boiled 
for  about  15  m.  in  a  diluted,  filtered  solution  of  the  jam  or 
jelly,  to  which  a  little  potassium  bisulfate  has  been  added. 
The  wool  is  then  boiled  with  water  containing  a  little  soap, 
and  if  it  has  been  colored  at  all  with  the  dye  it  is  digested 
with  dilute  ammonia,  which  will  dissolve  the  colors  fixed  in 
the  acid  bath.  The  fabric  is  then  removed  from  the  bath. 
Slightly  acidify  the  solution,  and  boil  with  a  new  piece  of 
the  fabric.  This  second  dyeing  will  fix  the  coal  tar  colors, 
but  will  not  fix  the  natural  fruit  colors.  There  are  a  few 
rather  uncommon  coloring  matters,  made  by  chemical 
methods  of  manufacture  from  vegetable  substances  like  cud- 
bear and  archil,  which  are  not  to  be  distinguished  from  ani- 
line dyes  by  any  method  of  dyeing.1 

Experiment  123.  To  detect  starch  in  jelly,  heat  an 
aqueous  solution  of  the  sample  nearly  to  the  boiling  point 
and  decolorize  by  the  addition  of  several  cubic  centimeters 
of  dilute  sulfuric  acid  and  afterwards  a  small  quantity  of 
potassium  permanganate.  Cool  the  solution,  filter  if  neces- 
sary, and  test  for  starch  by  the  iodine  reagent  as  usual.  Only 
a  small  quantity  of  starch,  but  enough  to  give  a  very  charac- 
teristic test,  is  normally  present  in  apple  juice.2 

For  testing  for  preservatives,  see  Chapter  XXV. 

1  Winton,  J.  Am.  Chem.  Soc.,  22,  1900,  p.  682. 

2  U.  S.  Dept.  Agric.,  Bu.  Chem.,  Bui.  65. 


COMPOSITION  AND   FOOD   VALUE  OF   FRUITS     221 

FRUIT   SIRUPS;  FLAVORING  EXTRACTS 

Many  fruit  sirups  are  upon  the  market,  which  are  pre- 
pared to  use  with  sugar  as  the  basis  of  beverages  either 
carbonated  or  otherwise.  These  sirups  may  be  made  from 
genuine  fruit,  sterilized  by  heating,  and  put  up  practically 
like  canned  fruit,  or  they  may  be  entirely  artificial,  like 
some  of  the  jellies  just  mentioned. 

Among  the  flavoring  extracts,  that  of  vanilla  and  lemon 
are  most  extensively  used.  Practically,  only  a  small  pro- 
portion of  the  vanilla  extract  on  the  market  is  made  wholly 
from  the  vanilla  bean,  as  this  is  very  expensive.  Most  of 
the  agreeable  flavor  of  vanilla  extract  is  due  to  the  presence 
of  a  body  called  vanillin,  C8H803.  Many  of  the  cheaper 
so-called  vanilla  extracts  on  the  market  are  made  by  the  use 
of  the  Tonka  bean,  which  contains  the  active  principal 
coumarin,  C9H602.  Some  manufacturers  claim  that  the 
quality  of  the  extract  is  improved  rather  than  otherwise  by 
the  use  of  the  Tonka  bean. 

Much  of  the  ordinary  "  compound  "  vanilla  extract  is  made 
by  the  use  of  the  artificial  vanillin,  and  the  artificial  cou- 
marin, with  some  coloring  matter  and  sugar,  added  to  a 
weak  alcoholic  tincture  of  the  Tonka  bean.1 

Experiment  123  a.  Place  some  extract  of  vanilla  in  an 
evaporating  dish  on  a  water  bath  and  evaporate  off  half  of 
the  liquid.  Add  cold  water  to  make  up  to  the  original 
volume.  By  this  treatment  the  alcohol  will  be  driven  off, 
and  in  the  watery  solution  that  is  left  the  substances  in  true 
vanilla  are  nearly  insoluble,  so  the  liquid  will  be  cloudy  and 
of  a  dirty  brownish  color.  The  artificial  extract,  on  the 
other  hand,  will  be  bright  and  clear. 

Experiment  123  b.     Add  a  little  of  a  solution  of  sugar  of 
lead  to  some  of  the  extract  of  vanilla.     The  true  vanilla 
aLab.  Inl.  Rev.  Dept.  Can.,  Buls.  89  and  114. 


222  SANITABY  AND   APPLIED   CHEMISTRY 

extract  will  give  an  abundant  yellowish  brown  precipitate 
and  a  pale  yellowish  liquid.  Upon  the  artificial  extract  the 
lead  solution  has  but  little  effect,  and  there  is  only  a  slight 
discoloration.  Another  test  is  to  notice  the  character  and 
color  of  the  foam  produced  on  shaking  some  of  the  artificial 
vanilla  extract.  The  bubbles  will  retain  their  bright  caramel 
color  till  the  last  ones  have  disappeared,  while,  if  the  extract 
is  genuine,  the  bubbles  are  much  lighter  in  color. 

Extract  of  lemon  should  contain,  according  to  the  U.  S. 
Pharmacopeia,  5%  of  oil  of  lemon,  and  to  keep  this  in  solu- 
tion will  require  alcohol  of  80  %  strength  by  volume.  Much 
of  the  extract  of  lemon  on  the  market  contains  only  a  trace 
of  the  oil,  and  less  than  40  %  of  alcohol.  A  sample  of  alcohol 
so  dilute  as  this  will  dissolve  only  a  very  small  quantity  of 
the  oil,  although  there  may  be  enough  to  give  the  extract  a 
slight  taste  and  odor.  Such  extracts  are  usually  colored 
yellow  by  the  use  of  coal  tar  dyes.1 

Experiment  123  c.  To  50  cc.  of  water  add  10  cc.  of  the 
extract  of  lemon  to  be  tested.  If  the  solution  becomes  milky, 
on  account  of  the  precipitation  of  the  oil  of  lemon,  it  is  of 
good  quality,  but  if  it  remains  clear  only  traces  of  the  oil  are 
present. 

Most  of  the  artificial  fruit  essences,  such  as  that  of  straw- 
berry, banana,  raspberry,  apple,  and  pineapple,  are  made  by 
ingeniously  combining  various  compound  ethers,  organic 
acids,  and  essential  oils.  These  are  usually  colored  with 
aniline  colors,  and  may  be  sweetened  by  the  use  of  glucose 
or  saccharin.1 

JU.  S.  Dept  Agric.,  Bu.  Chem.,  Bui.  65. 


CHAPTER  XVIII 
EDIBLE  FATS  AND  OILS 

THE  fats  used  in  the  manufacture  of  soap  have  already 
been  discussed,  but  the  importance  of  certain  fats  and  oils 
in  food  products  warrants  some  further  attention  to  them  in 
this  connection.  The  facility  with  which  a  fat  saponifies 
(see  p.  98)  is  of  great  importance  in  the  process  of  digestion. 
The  fats  are  insoluble  in  water,  but  readily  soluble  in  ether, 
chloroform,  oil  of  turpentine,  and  similar  solvents. 

Like  starch  and  sugar,  the  fats  do  not  directly  form 
muscular  tissue,  but  they  have  2^  times  the  power  to 
maintain  the  heat  and  activity  of  the  body  that  the 
carbohydrates  possess.  There  seems  to  be  little  difference 
whether  the  fat  comes  from  a  vegetable  or  an  animal 
source. 

The  amount  of  fat  existing  in  some  food  products  is 
as  follows:  — 

From  vegetable  sources :  — 

PEE  CENT  PEE  CENT 

Almonds 64.0  Sunflower  seed     .     .     .  20.5 

Peanuts 41.6  Oatmeal 6.0 

Olives  (pulp)   ....     66.4  Indian  corn  (white) .     .  4.2 

Cacao 44.0  Wheat  bran     ....  4.0 

Flax  seed 38.0  Peas 2.6 

Cocoanut 68.7  Wheat  flour     ....  1.0 

Cotton  seed      ....    20.1 

223 


224  SANITARY   AND   APPLIED   CHEMISTRY 

From  animal  sources  :  — 

PEE  CENT  Pis  CENT 

Butter 84.4  Poultry 16.3 

Bacon 65.0  Mackerel 13.0 

Mutton  chop    ....     35.0  Eggs  (whole)  ....     11.0 

Cheese 30.0  Cow's  milk 4.0 

When  fat  is  deposited  in  the  body  beneath  the  skin  it 
keeps  in  the  warmth  of  the  body.  The  fat  wherever  depos- 
ited may  be  reabsorbed  into  the  blood,  and  thus  keep  up 
the  animal  heat  for  a  long  period  even  when  food  is  not 
taken.  This  is  the  case  with  animals  which  hibernate  for 
several  months. 

The  demand  for  some  of  the  oils  has  been  constantly 
increasing.  Previous  to  1870  it  was  quite  a  problem  to  the 
cotton  planters  how  they  should  dispose  of  their  cotton 
seed,  while  to-day  the  oil  extracted  from  it  finds  numerous 
uses.  A  large  quantity  is  exported  to  Europe,  where  it 
is  used  in  the  manufacture  of  soaps  and  butterine,  and  oc- 
casionally as  an  adulterant  for  olive  oil.  Cotton-seed  oil  is 
used  in  the  United  States  in  canning  factories,  in  the  pres- 
ervation of  fish,  in  the  manufacture  of  "  cottolene,"  butter- 
ine, and  soap,  and  for  the  preparation  of  salad  dressing. 
The  cotton-seed-oil  product  of  1900  was  93,325,729  gal.  and 
only  53  %  of  possible  product  was  produced. 

The  oil  of  the  cocoanut  is  also  exceedingly  valuable,  both 
for  cooking  and  in  the  manufacture  of  soap.  It  is  imported 
from  various  tropical  countries,  especially  Ceylon  and  the 
East  Indies.  Unfortunately,  the  oil  soon  becomes  rancid, 
and  therefore  it  is  more  extensively  used  for  food  in  the 
countries  where  it  can  be  freshly  obtained  than  elsewhere. 

LARD 

The  "  rendered  "  fat  of  the  hog  has  the  general  name  of 
lard,  but  there  are  several  different  grades  made  at  the 
packing-house.  The  lowest  grade,  known  as  "  steam-ren- 


EDIBLE  FATS   AND   OILS  225 

dered"  lard,  or  "prime  steam  lard,"  is  extracted  from  the 
stock  by  admitting  steam  to  the  tank  under  a  pressure  of 
40  to  50  Ib.  The  object  of  cooking  lard  or  suet  material 
is  to  break  the  membranous  cells,  thus  allowing  the  fat  to 
escape,  and  to  heat  the  small  quantity  of  the  nitrogenous 
portion  that  may  remain  in  the  finished  product  so  that  it 
will  not  readily  decompose. 

A  "  refined  lard "  is  sometimes  made  from  the  "  prime 
steam  lard "  by  heating  it  in  a  tank  to  170°  F.  and  blowing 
in  air  for  some  time  to  remove  moisture.  It  is  then  bleached 
at  a  temperature  of  150°  to  165°  F.,  by  agitation  with  Fuller's 
earth  (clay  of  a  peculiar  composition),  and  filtered  through 
a  filter  press.  The  final  operation  in  the  manufacture  con- 
sists of  cooling  rapidly,  either  by  agitating  in  a  tank  sur- 
rounded by  cold  water,  or  by  running  the  lard  on  to  a  large 
roll,  which  is  filled  with  ice-cold  brine,  and  which  slowly 
revolves. 

Kettle  "  rendered  "  lard  is  that  which  is  made  in  kettles 
heated  externally,  and  corresponds  to  ordinary  household 
lard.  The  best  grade  of  "  leaf  lard  "  belongs  to  this  class. 
The  material,  which  has  been  thoroughly  washed,  is  heated 
at  as  low  a  temperature  as  possible  to  secure  the  result,  in 
steam-jacketed  kettles,  and  when  fully  rendered  is  drawn 
off  into  a  settling  tank,  before  being  filled  into  packages  for 
shipping.  The  "  scrap  "  remains  in  the  bottom  of  the  ren- 
dering kettle,  and  is  worked  over  again. 

The  method  of  making  "  neutral  lard,"  which  is  made 
from  leaf  lard  principally,  is  described  under  oleomargarine 
(Chapter  XXI).  As  it  is  not  fully  heated,  its  keeping  quali- 
ties are  not  good,  and  it  must  be  kept  in  cold  storage. 

Lards  are  sometimes  "  stiffened"  so  that  they  will  not 
melt  so  readily  in  a  warm  climate,  and  if  this  is  done  by 
the  addition  of  lard  stearin  it  is  not  considered  an  adultera- 
tion, but  the  use  of  the  oleostearin  from  beef  should  be 
considered  an  adulteration. 


22»5 


SANITARY   AND  APPLIED   CHEMISTRY 


"COMPOUND   LARD,"   "COTTOLENE,"   "COTTOSUET" 

There  are  a  number  of  products  on  the  market  which  do 
not  pretend  to  be  lard,  but  are  made  to  use  for  the  same 
purposes,  and  can  be  sold  at  a  lower  price.  Different  mix- 
tures of  fats  are  used  for  the  trade  of  different  countries, 
and  for  summer  and  winter  trade.  The  chief  materials 
used  are :  cotton-seed  oil,  oleostearin,  tallow,  and  sometimes 
lard.  These  materials  are  each  carefully  bleached  before 
being  mixed. 

THE  COMPOSITION  AND  FOOD  VALUE  OF  NUTS 

Within  the  last  few  years  nut  preparations  have  ap- 
peared on  the  market,  so  that  their  use  as  food  should  be  no 
longer  ignored.  Nuts  have  a  much  higher  nutritive  value 
than  fruits,  as  can  be  readily  seen  from  their  composition.1 


NUTS  AS  PURCHASED 

REFUSE 

WATER 

PRO- 
TEIN 

FAT 

TOTAL 
CARBO- 

HTDKAR 

ASH 

Almonds  .... 

45.0 

2.7 

11.6 

30.2 

9.5 

1.1 

Chestnuts     .     .    . 

16.0 

37.8 

5.2 

4.5 

35.4 

1.1 

Cocoanuts     .     .     . 

48.8 

7.2 

2.9 

25.9 

14.3 

.9 

Hickorynuts      .     . 

62.2 

1.4 

5.8 

25.5 

4.3 

.8 

Pecans     .... 

53.2 

1.4 

5.2 

33.3 

6.2 

.7 

Peanuts  .... 

24.5 

6.9 

19.5 

29.1 

18.6 

1.6 

Since  they  contain  a  large  amount  of  fat,  various  nut 
preparations  are  used  as  substitutes  for  butter.  On  account 
of  the  fact  that  nuts  are  not  readily  digested  in  the  stomach, 
the  attempt  has  been  made,  and  with  considerable  success, 
to  improve  the  product,  by  crushing  and  removing  the  excess 
of  oil  and  cellulose. 

Chestnuts,  which  are  used  very  extensively  as  food  by  the 

i  U.  8.  Dept  Agric.,  Office  Exp.  Sta.,  Bui.  28. 


EDIBLE  FATS   AND  OILS  227 

peasants  of  southern  Europe,  have  been  mentioned  under 
the  starchy  foods. 

In  the  almond-producing  countries  the  nut  is  eaten  both 
green  and  dry.  When  the  skin  has  been  softened  by  soak- 
ing for  some  time  in  warm  water,  it  may  be  removed  and 
the  nuts  are  said  to  be  "  blanched." 

It  is  interesting  to  note  that  there  are  two  kinds  of 
almonds,  the  sweet  and  the  bitter,  both  of  which  contain 
a  peculiar  ferment  called  "emulsin."  The  bitter  almond 
contains,  in  addition  to  this,  an  interesting  "  glucoside " 
known  as  amygdalin,  C^H^NOn  +  3  H20.  This,  in  the 
presence  of  water,  is  broken  up  by  the  emulsin  into  glucose, 
benzoic  aldehyde,  and  hydrocyanic  acid,  HCK  It  is  on  ac- 
count of  the  formation  of  this  latter  compound  that  bitter 
almonds  are  poisonous.  Amygdalin  is  also  obtained  from 
the  seeds  of  plums,  peaches,  cherries,  apples,  etc. 

The  cocoanut  is  probably  the  most  important  of  any 
nuts  to  a  large  number  of  people.  As  the  edible  part  or 
meat  contains  about  50%  of  oil,  th%  abundance  of  nutrient 
material  can  be  readily  appreciated.  Each  tree  yields  from 
80  to  100  nuts  a  year,  and  will  continue  to  bear  for  at  least 
two  generations.  The  importance  of  the  oil  in  various  in- 
dustries, such  as  that  of  soap  and  candle  making,  should  not 
be  overlooked. 

The  peanut,  although  not  properly  a  nut,  as  it  belongs  to 
the  leguminous  family,  since  the  edible  portion  contains 
about  38%  of  oil,  may  properly  be  considered  here.  As  it 
contains  about  25%  of  albuminoids,  and  considerable  starch, 
it  very  deservedly  is  coming  into  more  general  use  both  as  a 
food  for  man  and  for  cattle.  Three  hundred  million  pounds 
of  peanuts  are  grown  annually  for  use  in  the  United  States. 
The  principal  peanut-producing  states  are  Virginia  and  North 
Carolina.  As  sweet  almonds  and  peanuts  resemble  meat  in 
their  high  proteid  and  fat  content,  they  may  be  used  to  a 
certain  extent  to  take  the  place  of  meat. 


CHAPTER  XIX 
NITROGENOUS  FOODS 

IN  Chapter  X  it  is  stated  that  foods  are  divided  into 
two  general  classes,  carbohydrate  and  nitrogenous,  and  that 
the  carbohydrate  foods  contain  sugars,  starches,  dextrins, 
and  fats,  and  also  that  there  are  many  foods  that  contain 
both  classes  of  nutritive  materials.  The  relation  between 
these  different  foods  may  be  seen  by  comparing  the  composi- 
tion of  the  cereals  and  the  leguminous  foods. 

If,  however,  we  wish  to  make  use  of  a  concentrated  nitrog- 
enous food,  it  is  possible  to  utilize  the  system  of  some  animal 
that  subsists  on  vegetable  food,  and  so  we  use  as  nitroge- 
nous foods,  beef,  mutton1,  lean'  pork,  fish,  oysters,  poultry, 
game,  milk  and  its  products,  and  eggs.  Of  all  these,  beef 
may  be  regarded  as  the  most  typical  nitrogenous  food,  and 
it  is,  no  doiibt,  the  most  valuable  meat  for  all  purposes. 

Animal  foods  leave  comparatively  little  residue,  as  they 
are  practically  completely  digested ;  they  form,  then,  a  con- 
centrated food.  Not  only  are  the  animal  foods  of  agreeable 
flavor,  but  they  contain  mineral  salts,  which  are  of  great 
value  in  the  nutrition  of  the  body. 

"  Since,  in  some  way  as  yet  unknown  to  us,  nitrogen  is 
essential  to  living  matter,  such  substances  as  contain  this 
element  in  an  available  form  are  of  first  importance.  Some, 
as  albumen,  are  so  closely  allied  to  human  protoplasm  that 
they  probably  need  only  to  be  dissolved  to  be  at  once  assimi- 
lated. Others,  as  gluten  and  similar  vegetable  products, 
undergo  a  still  greater  change ;  while  still  others,  as  gelatin, 

228 


NITROGENOUS   FOODS  229 

have  a  less  profound  but  marked  effect  in  protecting  the 
tissues  from  waste.  Still  other  nitrogenous  substances, 
as  the  alkaloids,  seem  to  affect  the  nerve  tissue  for  good  or 
ill.  The  enzymes,  '  ferments '  in  part,  of  the  older  nomen- 
clature, are  also  highly  nitrogenous  substances,  present  in 
some  form  in  nearly  all  the  foodstuffs  of  natural  origin.  The 
nearer  the  composition  of  the  food  approaches  to  the  proto- 
plasmic proteid,  presumably  the  greater  its  food  value,  since 
each  cleavage,  each  hydrolysis,  each  step  in  the  breaking 
down  of  the  highly  complex  molecule,  consisting  of  hundreds 
of  atoms,  is  supposed  to  liberate  stored  energy.  Therefore 
it  is  not  a  matter  of  indifference  in  what  form  this  essential 
is  taken." 1 

CLASSIFICATION   OF    NITROGENOUS   FOODS 

The  following  is  a  convenient  classification  of  nitroge- 
nous bodies  that  occur  in  food.2 

I.  Proteids.  These  bodies  contain  nitrogen,  oxygen,  hy- 
drogen, carbon,  and  sulfur,  and  are  capable  of  being  con- 
verted, in  the  body,  into  proteoses  and  peptones.  They 
may  be  present  in  either  animal  or  vegetable  food.  Under 
this  general  head  the  following  divisions  are  made :  — 

1.  Albumins,  which  occur  in  eggs,  milk,  cereals,  etc. 

2.  Globulins,  which  occur  in  serum,  in  blood,  as  myosin 
in  meat,  as  vitellin  in  egg  yolk,  and  as  vegetable  vitellin  in 
cereals  and  in  peas,  beans,  etc. 

3.  Albuminates,  occurring  in  casein  of  milk,  in  peas  and 
beans,  and  in  almonds. 

4.  Proteoses,  which  occur  in  sour  milk,  ripened  cheese, 
and  wheat  flour. 

5.  Peptones,3  which  are  found  in  meat. 

1  Richards  and  Woodman,  "Air,  "Water,  and  Food,"  p.  142. 

2  Leach,  "  Food  Inspection  and  Analysis,"  pp.  36-41.  (From  Watts's 
Diet,  of  Chem.  Vol.  IV.)  8  Found  only  in  small  quantities. 


230  SANITARY   AND   APPLIED   CHEMISTRY 

6.  Insoluble  proteids,  such  as  fibrin  and  myosin,  in  ani- 
mal foods  and  gluten  in  wheat. 

II.  Albuminoids.     These  are  much  like  the  proteids,  and 
may  be  divided  into,  — 

1.  Collagen,  which  composes  the   fibers  of    connective 
tissues. 

2.  Gelatin,  which  is  made  by  boiling  bones. 

3.  Mucin,  which  is  found  in  meat  and  also  in  mucus. 

4.  Nuclein,  which  occurs  in  the  nuclei  of  cells  in  the 
egg  yolk  and  milk. 

5.  Chondrin,  a  substance  that  may  be  obtained  from  car- 
tilage by  long  boiling. 

6.  Elastin,  which  forms  the  elastic  fibers  of  connective 
tissue. 

III.  Amides,    amido-acids,    and    allied    products,    in- 
clude cholin  (C3H15N03),  betain  (C5HUN02),  and  asparagin 

(C4H8N208). 

IV.  Alkaloidal  substances,  such  as  those  occurring  in 
the  beverages,  tea,  coffee,  cocoa,  and  kola. 

V.  Nitrogen,  as  nitrates. 

VI.  Nitrogen,  as  ammonia. 

VII.  Lecithin  (C^HgoNPOg),  which  is  found  in  egg  yolk, 
cereals,  and  legumes. 

"  The  function  of  the  albuminous  substances  is  probably 
threefold,  as  they  contribute  to  the  formation  and  repair  of 
the  tissues  and  fluids  of  the  body,  and  in  a  special  manner 
of  the  nitrogenous  tissues ;  they  regulate  the  absorption  and 
utilization  of  oxygen,  and  so  play  an  important  part  in  the 
chemistry  of  nutrition ;  and  under  special  conditions  they 
may  also  contribute  to  the  formation  of  fat,  and  to  the  de- 
velopment of  muscular  and  nervous  energy,  and  to  the  pro- 
duction of  heat."  1 

1  L  B.  Yeo,  "Food  in  Health  aud  Disease,"  p.  13. 


NITROGENOUS   FOODS  231 

The  structure  of  lean  meat  may  be  compared  to  bun- 
dles of  tubes  or  fibers  filled  with  rich  nitrogenous  juices. 
These  fibers  are  soft  and  tender  in  the  young  animal,  but 
with  age  the  muscles  become  toughened  and  more  firmly 
bound  together.  This  muscular  tissue  is  divided  into  two 
classes :  the  voluntary,  or  striated  muscles,  like  those  of  the 
shoulder ;  and  the  involuntary,  or  nonstriated  muscles,  like 
those  of  the  heart.  The  latter  are  not  considered  so  valuable 
for  food.  The  substance  of  the  connective  tissue  consists 
chiefly  of  the  albuminoids,  elastin,  and  collagen,  the 
latter  being  a  substance  which  is  changed  by  boiling 
with  water  or  treatment  with  acids  into  gelatin.  The  pro- 
teids  of  the  meat  juice  consist  chiefly  of  the  globulin  myosin, 
muscle  albumen,  and  muscle  pigment. 

In  the  living  muscle,  while  there  are  no  peptones,  the  fer- 
ment pepsin  is  present,  and  after  death,  by  the  action  of  the 
pepsin  in  the  presence  of  lactic  acid,  a  portion  of  the  normal 
proteid  of  the  muscle  seems  to  undergo  a  kind  of  digestion, 
so  that  in  the  meat  traces  of  both  peptones  and  proteoses 
are  found.  Ordinarily  these  latter  bodies  are  the  result  of 
some  digestive  action  on  higher  proteids.  We  have  also 
present  in  the  meat,  creatin,  xanthin,  etc.,  which  are  known 
as  flesh  bases.  It  is  evident  that  the  nitrogenous  bodies 
constitute  the  bulk  of  lean  meat,  while  the  carbohydrates 
are  almost  entirely  lacking.  It  should  be  noted  that  the 
different  "  cuts  "  of  meat  have  entirely  different  food  values. 
It  is  not  possible  by  a  chemical  analysis  to  distinguish  be- 
tween the  meat  from  different  animals. 

Since  myosin  has  the  property  of  clotting  after  death, 
the  meat  undergoes  the  process  of  muscle  stiffening  or 
rigor  mortis.  If  the  meat  is  allowed  to  stand  till  this  con- 
dition has  passed  off,  on  account  of  the  resolution  of  a  part 
of  the  myosin,  and  the  partial  digestion  from  the  pepsin  pres- 
ent, it  becomes  tender  again.  This  process  should  not  be 


232  SANITARY   AND   APPLIED  CHEMISTRY 

allowed  to  go  too  far,  or  the  meat  will  become  "  high,"  and 
have  a  disagreeable  odor  and  flavor. 

The  character  of  the  extractives  very  much  modifies  the 
flavor  of  the  meat,  and  if  these  extractives  are  removed 
by  prolonged  boiling  or  digestion  with  water,  the  meat  has 
very  little  taste.  The  following  analyses  show  the  propor- 
tion of  the  important  ingredients  in  one  kind  of  meat :  — 

EFFECT   OF   COOKING 

LEAN  BEEF  l  RAW  BEEF  2  ROASTED  BEEF  a 

Proteid    ....  18.36  Water    .     .    70.88  55.39 

Gelatin  (Collagen?)  1.64  Nitrogenous 

Fat 90                   matter      22.51  34.23 

Extractives  .    .     .    1.90  Fat    .     .     .    4.52  8.21 

Ash 1.30  Extractives      0.86  0.72 

Water      ....  75.90  Min'l  Salts      1.23  1.45 

THE  USE   OF  ANIMAL   FOOD 

According  to  Mulhall  the  quantity  of  animal  food  used 
per  year  per  capita  is  as  follows  in  the  different  countries : 

POUNDS  POCMDB 

United  States      120  Scandinavia 67 

Great  Britain       105  Austria 64 

France 74  Spain        49 

Germany 69  Russia 48 

Belgium  and  Holland  ....      69  Italy 43 

COOKING    OF    MEAT 

The  general  object  of  cooking  food  has  already  been  dis- 
cussed (p.  120).  In  the  case  of  meat,  a  high  temperature  not 
only  softens  the  fibers  and  makes  the  product  more  agree- 
able to  the  taste,  but  it  is  only  in  this  way  that  we  can  be 
sure  that  pathogenic  bacteria  and  parasites  are  destroyed. 

The   following  processes  of  cooking  may  be  applied  to 
meat :  boiling,  roasting,  broiling,  baking,  stewing,  frying. 
1  Biachoff  &  Voit  »  K6nig. 


NITROGENOUS   FOODS  233 

In  the  cooking  of  meat  it  is  essential  to  know  the  object 
desired  in  the  process.  If  we  want  an  extract,  the  meat 
should  be  placed  in  cold  water  and  kept  at  a  temperature 
below  160°  F.,  for  several  hours,  with  the  addition  perhaps 
of  a  little  salt.  This  is  the  method  for  extracting  the  nutri- 
tive material  for  making  soup.  Recent  experiments,  how- 
ever, show  that  there  is  not  as  much  difference  in  the  com- 
position of  meats  immersed  in  cold  water  and  then  cooked 
at  85°  C.,  and  those  plunged  at  once  in  boiling  water  and 
cooked  at  85°  C.,  as  was  formerly  supposed.  If,  on  the  other 
hand,  we  desire  to  retain  the  rich  juices  in  the  meat,  it  must 
be  heated  as  quickly  as  possible,  especially  on  the  outside,  so 
as  to  prevent  the  escape  of  these  juices  with  their  accompany- 
ing flavors.1  This  is  done  most  practically  by  broiling  the 
meat,  and  to  some  extent  by  baking  or  roasting.  The  process 
of  frying  meat  is  very  unsatisfactory  and  affords  a  product 
that  is  tough  and  unwholesome. 

The  greater  part  of  the  proteids,  both  animal  and  vege- 
table, are  coagulated  at  about  170°  F.  Fats  are  not  as  much 
affected  by  heat  as  carbohydrates  and  proteids,  but  when  they 
are  heated  to  a  high  temperature,  they  are  liable  to  become 
partially  decomposed.  It  is  reasonable  then  to  suggest  that 
if  meat  is  boiled,  in  order  to  retain  the  juices  which  it  con- 
tains, the  meat  should  be  plunged  into  boiling  water  for  a 
few  minutes,  thereby  sealing  up  the  juices  within  the  fibers, 
then  lowering  the  temperature  for  the  thorough  cooking 
of  the  meat.  If  a  small  quantity  of  water  is  used,  less  of 
the  soluble  material  will  be  extracted.  The  average  loss 
in  weight  when  meat  is  cooked  in  hot  water  is  about  34%. 2 

In  the  process  of  roasting,  especially  when  the  meat  is 
"  basted,"  the  same  method  for  sealing  up  the  tubes  is  used, 
so  that  the  j  uices  may  be  retained.  This  is  still  better  accom- 

1  Grindley,  U.  S.  Dept.  Agric.  Office  Exp.  Sta.,  Bui.  162. 

2  LOG.  cit. 


234  SANITARY   AND   APPLIED   CHEMISTRY 

plished  in  broiling  or  grilling,  because  the  heat  that  is  at  first 
applied  is  more  intense  and  later  the  meat  has  an  opportu- 
nity to  cook  toward  the  interior,  so  that  the  flavor  is  supe- 
rior and  the  agreeable  extractives  are  largely  retained. 

In  stewing  or  preparing  a  "  pot  roast, "  as  the  heat  is  low 
and  long  continued,  and  as  the  juices  that  happen  to  be 
extracted  are  all  served  with  the  meat,  the  process  is  very 
satisfactory.  If  the  temperature  in  stewing  is  not  allowed 
to  rise  above  180°  F.,  the  meat  will  fall  apart  readily,  and 
the  proteids  will  not  be  coagulated,  hardened,  or  rendered 
indigestible.  It  is  an  interesting  fact  that  while  vegetable 
foods  take  up  water  when  they  are  boiled,  animal  foods 
actually  lose  water.  According  to  some  recent  investi- 
gations 1  the  average  amount  of  water  in  14  samples  of  un- 
cooked meats  was  70.08  %,  while  in  the  31  samples  cooked 
in  hot  water  it  was  only  57.50  %. 

BEEF    EXTRACTS 

There  has  been  much  discussion  as  to  the  nutritive  value 
of  beef  extracts,  and  the  conclusion  seems  to  be  that  the  com- 
mercial extracts  are  not  as  valuable  as  a  simple  beef  extract 
made  by  slightly  broiling  the  beef  and  then  squeezing  out  the 
juice.  It  is  a  mistake  to  suppose  that  1  Ib.  of  beef  extract 
contains  the  soluble  constituents  of  20  to  30  Ib.  of  lean  beef, 
and  that  as  it  is  supposed  Baron  Liebig  once  taught  it  is 
equal  in  nutritive  value  to  this  amount  of  beef.  This  extract 
lacks  many  of  the  most  nutritious  constituents,  especially 
the  proteids,  and  probably  acts  more  as  a  stimulant  and  a 
substance  to  rouse  the  appetite  for  other  foods,  than  as  a 
true  food.2  There  are  also  preparations  on  the  market  which 
consist  of  extract  of  beef,  to  which  some  of  the  meat  fiber 
has  been  added.  They  are  shown  by  analysis  to  contain 
some  proteid.  "  Beef  juices,"  which  should  be  made  by 
1  Loc.  cit.  a  Church,  "  Food,"  p.  183. 


NITROGENOUS    FOODS  235 

expression  of  the  juice  from  the  raw  or  slightly  heated  meat, 
contain  considerable  proteid  and  are  valuable  nutrients. 

Referring  to  the  fluid  meat  preparations,  Thompson !  says : 
"Usually  they  are  tired  of  soon,  and  do  not  support  life 
long,  for,  beyond  the  means  employed  of  condensation  of 
food  by  evaporation  of  water  and  compression,  it  is  not 
possible  to  'concentrate'  nourishment  very  much.  Making 
food  assimilable  and  more  useful  is  another  matter  from 
concentrating  it  in  the  sense  that  it  can  be  made  to  sup- 
port an  able-bodied  man  and  supply  him  with  energy  for 
a  day's  work,  for  example,  of  mountain  climbing." 

The  different  varieties  of  meat  do  not  differ  in  their  com- 
position as  much  as  might  be  supposed.  Some  contain  more 
water,  some  contain  more  fat.  The  fats,  it  will  be  remem- 
bered, belong  to  the  same  class  as  the  carbohydrates;  that  is, 
they  are  "  work  and  heat  producers,"  and  not  "tissue  formers  " 
like  the  nitrogenous  foods.  Comparative  analyses  show 
that  when  fat  is  deposited  in  a  muscle,  it  replaces  water,  and 
not  proteid,  so  the  gain  in  nutritive  matter  is  not  attained  by 
the  loss  of  nitrogenous  materials.  Lean  beef  may  contain 
19  %  of  nitrogenous  matter  and  72  °/0  of  water.  Fat  pork 
only  contains  9.8%  of  nitrogenous  matter  and  nearly  40% 
of  water.  Some  of  these  foods  are  more  digestible,  of  course, 
than  others.  For  instance,  mutton  is  said  not  to  be  as  readily 
assimilated  as  beef.  Veal  is  liable  to  produce  intestinal 
disorders.  Since  fish2  is  both  a  cheap  and  nutritious  food, 
it  should  be  used,  in  many  localities,  in  larger  quantities  than 
at  present.  The  United  States  government  is  making  praise- 
worthy efforts  to  introduce  the  common  varieties  of  food 
fishes  in  all  the  waters  of  the  country,  so  that  fish  may  be  more 
abundant  and  cheaper.  If  we  compare  the  analysis  of 
fish  with  that  of  meat,  we  notice  that  the  nitrogenous  part 

1  "  Practical  Dietetics,"  p.  118. 

2  Bui.  28,   Office  of  U.  S.  Dept.  Agric.  Exp.  Stations. 


236  SANITARY   AND   APPLIED   CHEMISTRY 

of  fish  affords  more  of  the  gelatin-yielding  matter — that  is, 
the  collagen  —  and  less  extractives  than  meat.  There  is  also 
much  less  haemoglobin  in  the  flesh  and  blood  of  fish  than 
in  meat,  so  the  flesh  of  most  fish  is  of  a  light  color.  The 
mineral  matter  is  usually  high,  and  contains  a  considerable 
quantity  of  phosphates.  Fish  does  not  improve,  like  meat, 
by  being  kept,  even  on  ice,  but  it  rather  deteriorates. 

Fish  may  be  conveniently  divided  into  two  classes, — the 
lean  and  fat.  Some  examples  of  these  are  the  following: *  — 

PER  CENT  OF  FAT 

FAT  FISH                            SOMEWIIAT  FAT  LKAH 

Eels 18     Halibut    ..    2  to  10    Cod 0.4 

Salmon     ...     12     Mackerel      .      2  to  9  Haddock    ...  0.3 

Herring     ...      8     Mullet      .     .      2  to  3  Trout    ....  2.1 

Turbot.     ...     12  Bass      ....  2.8 

There  is  more  waste  matter,  such  as  skin  and  bones,  in 
fish  than  in  meat,  and  the  per  cent  of  water  is  very  high, 
especially  in  the  lean  varieties.  As  fish  contains  con- 
siderable gelatin-yielding  substances,  it  loses  more  on 
boiling  than  does  meat,  hence  this  is  not  a  good  method  for 
cooking  fish. 

Oysters  are  easily  digested,  but,  as  they  contain  88% 
of  water,  they  are  not  regarded  as  a  valuable  food  from  a 
purely  nutritive  standpoint.  They  contain  both  carbo- 
hydrates (glycogen)  and  nitrogenous  matter,  though  it  is 
probable  that  the  latter  is  not  all  present  in  the  form  of 
proteids.  Most  of  the  other  shellfish  are  not  as  digestible 
as  oysters. 

Meats  are  liable  to  be  dangerous  to  consumers  on  account 
of  the  diseases  with  which  the  animals  have  been  affected. 
This  is  especially  the  case  with  pork,  which  is  liable  to  be 
infected  with  tapeworms,  trichinae, '  and  other  parasites. 
The  only  safe  method  to  be  employed,  if  we  use  pork,  is  to 
1  Farmer's  Bui.  86,  U.  S.  Dept.  Agric. 


NITROGENOUS    FOODS  237 

see  that  it  is  thoroughly  cooked.  Ham,  for  instance,  unless 
boiled  for  a  long  time,  is  not  heated  to  a  high  enough 
temperature  to  destroy  the  parasites.  Most  of  the  varieties 
of  game  are  wholesome,  and,  where  abundant  enough  to  be 
reasonable  in  price,  are  very  important  foods.  The  same 
may  be  said  of  the  so-called  sea  foods.  Many  of  these 
furnish  the  proteid  bodies  in  a  very  concentrated  form,  so 
if  we  use  this  kind  of  food  exclusively,  it  is  not  a  well- 
balanced  ration.  It  is  a  familiar  fact  that  sailors  on 
long  voyages  or  those  living  in  nearly  inaccessible  regions 
suffer  severely  from  scurvy  if  they  are  obliged  to  subsist 
on  salt  meats  without  potatoes  or  other  vegetables. 

Experiment  124.  Procure  some  "Hamburg  steak,"  and 
weigh  out  about  25  grams.  Put  this  into  100  cc.  of  boiling 
distilled  water  and  boil  for  30  m.  Keep  the  volume  of 
the  liquid  constant  by  the  addition  of  more  water.  Filter, 
while  hot,  through  a  cloth,  and  wash  with  hot  water  till  the 
filtrate  measures  200  cc.  Evaporate  this  filtrate  in  a 
weighed  dish,  to  dryness,  cool,  and  weigh,  and  from  this 
calculate  the  per  cent  of  soluble  matter  obtained. 

Experiment  125.  Weigh  out  a  similar  amount  of  steak  and 
add  to  it  2  grams  of  salt.  Carry  out  the  experiment  as  in  Ex- 
periment 124,  subtract  the  2  grams  of  salt  from  the  weighed 
residue,  and  calculate  the  per  cent  of  soluble  material. 

Experiment  126.  Weigh  about  25  grams  of  steak,  place  it 
in  a  beaker  in  100  cc.  of  cold  water,  and  digest  on  a  water 
bath  at  a  temperature  not  above  80°  C.  (176°  F.)  for  2  hr., 
then  filter,  and  proceed  as  in  Experiment  124.  Find  the 
per  cent  of  soluble  material. 

Experiment  127.  Weigh  out  25  grams  of  steak,  and  treat 
as  in  the  previous  experiment,  except  add  2  grams  of  salt. 
Find  the  per  cent  of  soluble  material,  after  subtracting  the 
2  grams  of  salt  added. 


CHAPTER   XX 
EGGS 

As  the  egg  contains  all  the  substances  necessary  for  the 
development  of  the  chicken,  and  to  sustain  it  until  hatched, 
its  composition  is  of  special  interest.  Over  nine  billions  of 
eggs  are  produced  annually  in  the  United  States  (Clark) . 
Eggs  contain  much  proteid  and  mineral  matter,  which  is 
used  to  furnish  the  salts  of  the  bones,  especially  calcium 
phosphate,  and  also  fat,  one  of  the  most  concentrated  forms 
of  nutriment.  The  average  weight  of  a  hen's  egg 
is  60  g.  (2  oz.),  and  of  this  the  shell  weighs  6  g.,  the 
white  36,  and  the  yolk  18.  The  shell  consists  mainly  of  cal- 
cium carbonate. 

The  white  always  has  an  alkaline  reaction,  and  consists 
of  a  solution  of  proteid  inclosed  in  numerous  cells.  When 
the  egg  is  beaten  the  cells  are  ruptured  and  the  proteid  is 
set  free. 

EGG   WHITE 

According  to  Church1  egg  white  has  the  following  com- 
position :  — 

Water 84.8 

Albumin 12.0 

Fat,  sugar  extractives,  membranes      .        .        .          2.0 
Mineral  matter 1          1.2 

The  nitrogenous  material  or  albumin  consists  of  at  least 

four  distinct  compounds,  all  quite  complex  in  structure. 

These  contain  carbon,  hydrogen,  nitrogen,  sulfur,  phosphorus 

1  "  Foods,"  f.  160. 

238 


EGGS  239 

and  oxygen,  but  it  is  not  at  present  possible  to  state  their 
exact  formulae. 

EGG    YOLK 

The  yolk  is  much  richer  than  the  white,  as  the  following 
analysis  shows :  — 

Water              61.5 

Casein  and  albumin 15.0 

Oil,  lecithin,  etc.              30.0 

Pigment,  extractive,  etc. 2.1 

Mineral  matter        .......  1.4 

The  composition  of  the  white  and  yolk  together  as  com- 
pared with  meat  is  as  follows : 1  — 

£OO        MODEEATELY   LEAK    MEAT 

Water 73.7  73.0 

Proteid 14.8  21.0 

Fat 10.6  5.5 

Ash    ......  1.0  1.0 

So  eggs  may  with  propriety  be  used  to  supplement  food 
rich  in  carbohydrates  and  lacking  in  proteids  and  fat. 
Fat  ham  and  eggs  do  not  form  a  well-balanced  diet,  but 
potatoes  or  bread  with  eggs  form  a  good  diet.  It  is  esti- 
mated that  from  15  to  20  eggs  are  the  nutritive  equivalent  of 
2  Ibs.  of  medium  fat  meat. 

For  the  preservation  of  eggs,  a  large  number  of  methods 
have  been  proposed,  such  as  packing  in  bran,  coating  with 
vaseline  or  gelatin,  and  covering  with  brine  or  limewater. 
The  best  method,  however,  has  been  found  to  be  by  covering 
with  a  10%  solution  of  water  glass  (sodium  potassium 
silicate).2  As  these  eggs  break  readily  on  boiling,  they 
should  be  pierced  with  a  needle  before  being  put  into  the 
water. 

Desiccated  eggs  have  been  recently  put  upon  the  market. 
If  fresh  eggs  are  used  in  this  preparation,  there  is  no  reason 

1  Atwater,  Bui.  28,   Office  of  Exp.  Sta.  U.  S.  Dept.  Agric. 

2  Farmer's  Bui.  103,  Dept.  Agric. 


240  SANITARY   AND   APPLIED   CHEMISTBY 

why  it  should  not  be  possible  to  furnish  a  good  article  of 
diet,  when  the  water  has  been  driven  off  by  drying  in 
thin  layers,  in  a  current  of  warm  air.  The  temperature 
employed  is  one  that  will  give  as  rapid  drying  as  possible 
without  coagulating  the  albumin.  A  good  quality  of  dried 
egg  should  contain  7%  or  less  of  moisture,  37%  of  fat,  and 
about  30%  of  soluble,  coagulable  proteids. 

Most  of  the  so-called  "egg  substitutes"  and  "custard 
powders  "  consist  chiefly  of  starch,  dried  skimmed  milk,  and 
turmeric,  a  yellow  coloring  matter  or  Victoria  yellow ;  they 
are,  of  course,  worthless  as  "  substitutes." 

There  is  a  popular  notion  that  hard-boiled  eggs  are  not 
digestible,  and  experiments  made  with  eggs  in  the  stomach 
lead  to  the  same  conclusion.  Thus  eggs  slightly  boiled  have 
left  the  stomach  in  If  hr.,  raw  in  2^  hr.,  and  hard-boiled  in 
3  hr.  It  should  be  noted,  however,  that  raw  eggs  are  only 
partially  digested  in  the  stomach,  perhaps  because  they  do 
not  excite  the  flow  of  the  gastric  juice.  The  complete  diges- 
tion is  accomplished  farther  along  in  the  alimentary  canal. 

In  cooking  eggs,  especially  for  invalids,  they  should  be 
placed  in  water  at  170  °  to  180°  F.,  and  allowed  to  remain  for 
10  m.,  when  the  yolk  will  be  found  to  be  more  coagulated 
than  the  white.  The  egg  albumin  begins  to  coagulate  at 
134°  F.,  and  it  requires  some  time  to  heat  the  egg  throughout. 

A  convenient  method  for  cooking  eggs  without  the  use  of 
a  thermometer,  is  to  pour  a  quart  of  boiling  water  into  a 
bowl,  and  put  two  or  three  eggs  into  this  and  allow  them  to 
remain  for  ten  or  twelve  minutes.  The  yolk  actually  cooks 
more  readily  than  the  white,  and  by  this  process  the  eggs 
are  cooked  uniformly  throughout. 

Experiment  128.  Mix  some  egg  white  with  water,  add  a 
drop  or  two  of  nitric  acid,  and  notice  that  it  coagulates. 

Experiment   129.     Shake  some   egg  yolk    in  a  test  tube 


EGGS  241 

•with  ether,  decant  off  the  clear  liquid  into  a  glass  evaporat- 
ing dish  and  allow  to  evaporate  spontaneously.  The  egg  fat 
will  remain  in  the  dish. 

Experiment  130.  To  show  the  action  of  pepsin  on  eggs  use 
0.1  gram  of  pepsin  and  10  grams  of  boiled  disintegrated 
egg  albumin,  that  has  been  passed  through  a  sieve.  Make  an 
acidulated  water  with  5  cc.  of  concentrated  hydrochloric 
acid  in  300  cc.  of  water.  Dissolve  the  pepsin  in  100  cc.  of 
the  acidulated  liquid.  To  5  grams  of  the  disintegrated 
albumin,  in  a  100  cc.  wide-mouthed  bottle,  add  25  cc.  of  the 
solution  of  pepsin  and  40  cc.  of  the  acidulated  water.  Cork 
the  bottle  and  keep  it  in  a  water  bath  at  a  temperature  of 
52°  C.  for  an  hour,  and  note  the  result.  (L.  E.  Sayre.) 


CHAPTER  XXI 


MILK 

IN  its  composition  milk  suggests  blood;  that  is,  it  is  a 
thin  watery  fluid  in  which  various  bodies  are  held  in  sus- 
pension and  in  solution.  We  can  readily  see,  by  the  use 
of  the  microscope,  that  the  fat  globules  of  milk  are  thus 
held  in  suspension.  It  has  been  shown  that  the  richer  the 
milk  the  larger  these  fat  globules.  The  liquid  that  holds 
them  in  suspension  is  rich  in  nitrogenous  matter  and 
in  sugar.  As  will  be  seen  from  an  analysis,  milk  occupies 
an  intermediate  position  between  cereal  and  strictly  animal 
foods.  Of  the  cereal  class,  it  contains  milk  sugar  and 
fat;  while  of  the  animal  class  it  contains  casein  and 
albumin.  Milk  is  slightly  alkaline  in  reaction.  On  account 
of  the  cost  of  milk  in  many  cities,  the  poorer  classes  use 
only  limited  quantities.  For  instance,  in  London,  an  estimate 
made  some  time  since  showed  from  1|  to  1\  oz.  per  capita  was 
used  weekly,  while  in  Scotland  6£  pt.  was  used  per  week. 
The  composition  of  milk  from  different  animals  varies  con- 
siderably as  can  be  seen  by  an  inspection  of  the  table:1 — 


SPKC. 
GRAY. 

WATEB 

CASEIN 

ALBU- 
MIN 

TOTAL 
PROTKIDS 

FAT 

MILK 
SUGAR 

ABB 

Cow's 

1.0315 

87.17 

3.02 

.63 

3.66 

3.64 

4.88 

.71 

Human 

1.0290 

87.41 

1.03 

1.26 

2.29 

3.78 

6.21 

.31 

Goat's 

1.0306 

85.71 

3.20 

1.09 

4.29 

4.78 

4.46 

.76 

Sheep's 

1.0341 

80.81 

4.97 

1.65 

6.52 

6.86 

4.91 

.89 

Mare's 

1.0347 

90.78 

1.24 

.76 

1.99 

1.21 

6.67 

.36 

ABS'B 

1.0360 

89.64 

.67 

1.55 

2.22 

1.64 

5.99 

.51 

1  Konig. 

242 

MILK  243 

The  specific  gravity  of  milk  ranges  from  1.027  to  1.035. 
A  convenient  form  of  apparatus  to  use  in  determining  the 
specific  gravity  is  the  lactometer,  which  has  a  range  from 
1.015  to  1.040,  and  is  usually  standardized  at  60°  F.  (15°  C.) 

Experiment  131.  Test  a  sample  of  milk  by  a  hydrometer 
or  lactometer  to  determine  its  specific  gravity.  Readings 
taken  at  other  temperatures  than  15°  may  be  corrected  by 
a  table  that  has  been  prepared. 

The  lactometer  was  formerly  relied  upon  to  detect  the 
addition  of  water  to  milk,  but  since  the  cream  may  be  partially 
removed,  and  then  considerable  water  added  to  correct  the 
specific  gravity,  this  instrument  is  not  very  valuable,  ex- 
cept for  confirmatory  tests. 

By  the  saponification  of  butter  fat  the  following  compo- 
sition was  obtained : 1 — 

Butyric  acid 6.13      Oleic  acid 36.10 

Caproic,  caprylic,  and  capric  Glycerol  (calculated)  .     .     12.56 

acids 2.00  ,n«  q<> 

lUO.O^ 

Mynstic,palmitic,and  steanc 
acids 49.46 

These  results,  and  many  others  that  might  be  quoted, 
show  that  butter  fat  is  practically  a  mixture  of  various 
esters,  those  of  butyric,  palmitic,  and  oleic  acids  being  the 
most  abundant.  The  amount  of  stearic  acid  contained  in 
butter  is  probably  very  small.  The  first  four  constituents 
are  those  which  distinguish  butter  fat  from  ordinary  fats 
like  lard  or  tallow.  It  is  by  the  determination  of  the 
amount  of  these  that  the  chemist  is  able  to  distinguish 
between  genuine  butter  and  its  imitations. 

The  amount  of  fat  varies  from  3  %  to  6.5  %,  or  even  7  %, 
in  normal  milk.  In  some  countries  any  milk  having  less 
than  4  %  of  fat  is  considered  adulterated,  but  the  minimum 

1  James  Bell,  from  Allen's  "  Commercial  Organic  Analysis,"  Vol.  II, 
p.  181. 


244  SANITARY   AND   APPLIED   CHEMISTRY 

amount  allowed  in  many  cities  in  the  United  States  is  3  %. 
The  Secretary  of  Agriculture  in  consultation  with  the  Asso- 
ciation of  Official  Agricultural  Chemists  has  adopted  as  a 
"standard"  for  milk,  that  it  shall  contain  not  less  than 
12%  of  total  solids,  and  not  less  than  8.5  %  °f  solids 
not  fat,  nor  less  than  3.25  %  of  milk  fat.  The  fat  in  milk 
can  be  separated  for  laboratory  purposes  by  shaking  it  out 
with  ether,  and  then  allowing  the  ethereal  solution  to  evapo- 
rate. A  practical  method  for  the  determination  of  fat  is 
the  one  used  in  large  dairies;  that  is,  by  the  use  of  the 
Babcock  tester.  This  instrument,  invented  by  Professor 
Babcock  of  the  University  of  Wisconsin,  has  proven  of  im- 
mense value  to  the  dairy  interests,  as  it  is  possible  for  the 
producer,  as  well  as  the"  manufacturer,  to  know  exactly  the 
value  of  the  milk.  The  first  milk,  called  the  "  fore  milk," 
which  is  drawn  from  the  udder  of  the  cow,  is  poor  in  fat, 
because  the  fat  globules  have  risen  to  the  top ;  but  for  the 
same  reason,  the  "  strippings,"  or  last  of  the  milk  drawn, 
is  rich  in  fat. 

The  cream  may  be  raised  upon  the  milk  by  allowing  it  to 
stand  in  shallow  pans  for  a  long  time,  by  putting  it  in  deep 
vessels  and  keeping  it  at  a  comparatively  low  temperature, 
or  more  recently,  and  more  practically,  by  the  use  of  the 
"  separator."  This  is  nothing  but  a  centrifugal  machine  so 
arranged  that  the  lighter  cream  shall,  when  the  milk  is 
whirled  with  great  rapidity,  come  to  the  center  and  be  car- 
ried off  by  a  pipe,  and  the  heavier  milk  shall  be  thrown  to 
the  outside  by  the  same  motion,  and  carried  off  to  a  sepa- 
rate receptacle. 

There  is  a  fermented  beverage  known  as  "koumiss,* 
made  from  milk,  which  should  be  mentioned.  It  was 
originally  prepared  from  mare's  milk.  It  is  made  by  mix- 
ing milk  with  yeast  and  some  sugar,  putting  it  in  a  bottle, 
and  closely  corking  it.  Fermentation  takes  place  after 


MILK  245 

two  or  three  days,  and  the  beverage  is  fit  for  use.  It  is  used 
as  a  nourishing  tonic  for  invalids  and  seldom  contains  as 
much  as  2%  of  alcohol. 

Experiment  132.  Shake  a  few  cubic  centimeters  of  milk 
with  ether,  allow  the  ethereal  layer  to  separate  out,  draw 
it  off  with  a  pipette,  and  allow  it  to  evaporate  on  a  watch 
glass.  This  gives  quite  a  pure  grade  of  butter  fat. 

Experiment  133.  Determine  the  amount  of  butter  fat  in 
several  samples  of  whole  milk  by  the  use  of  the  Babcock 
tester.  By  the  action  of  oil  of  vitriol  on  a  measured  quan- 
tity of  milk,  a  great  amount  of  heat  is  evolved,  and  the 
mixture  turns  dark  brown  upon  the  addition  of  hot  water ; 
when  the  bottle  is  put  into  a  "centrifuge"  and  whirled 
rapidly,  the  fat,  which  is  lighter,  collects  in  the  narrow 
stem  of  the  bottle.  The  graduations  of  this  stem  have 
such  a  relation  to  the  quantity  of  milk  used  that  the  per 
cent  of  butter  fat  can  be  read  directly  upon  it. 

The  total  solid  matter  in  milk  is  also  of  use  to  the 
chemist  in  forming  an  opinion  as  to  whether  a  sample  has 
been  diluted  with  water  or  not.  The  lowest  amount  of 
solids  usually  permitted  in  normal  milk  is  12  %,  but  most 
milk  contains  from  1  to  3  %  more. 

Experiment  134.  Test  the  sample  of  milk,  the  specific 
gravity  of  which  has  been  already  determined  (Experiment 
131)  for  "  total  solids,"  by  weighing  a  small  glass  or  porcelain 
evaporating  dish  on  the  horn-pan  balance.  Weigh  into  this 
about  5  cc.  of  the  sample,  and  evaporate  for  about  2  hr.,  or 
till  perfectly  dry,  on  a  water  bath.  Weigh  the  residue,  and 
from  this  and  the  known  weight  of  the  milk,  calculate  the 
per  cent  of  total  solids.  Reserve  the  residue  for  Experi- 
ment 136. 

The  casein  of  milk  exists  apparently  in  the  fresh  sample 
as  a  soluble  compound  of  albumin  and  calcium  phosphate, 


246  SANITARY   AND   APPLIED   CHEMISTRY 

which  by  the  action  of  "  rennet,"  a  ferment  from  the  calf's 
stomach,  is  converted  into  an  insoluble  compound  known  as 
casein.  The  casein  precipitate  of  rennet  contains  from  1 
to  1.5%  of  ash,  consisting  almost  entirely  of  calcium  phos- 
phate. Lactic  acid  also  precipitates  the  casein,  but  the  pre- 
cipitate contains  less  ash  than  that  separated  by  rennet. 
Mineral  acids  also  precipitate  a  casein  containing  less  ash. 
The  proportion  of  albumin  in  milk  is  always,  according  to 
Blyth,  about  one  fifth  of  the  casein. 

The  proteids  of  milk  contain  about  80  %  of  casein,  which  is 
not  coagulated  by  heat  but  is  coagulated  by  acids,  about  15  % 
of  lactalbumin,  which  is  soluble  and  coagulates  by  heat  and 
forms  the  skin  on  boiled  milk,  and  a  few  minor  ingredients. 

In  the  souring  of  milk,  which  is  caused  by  certain  acid- 
forming  bacteria,  part  of  the  inilk  sugar  is  changed  into 
dextrose  and  galactose,  and  the  latter  sugar  changes  to  lac- 
tic acid:  — 
Ci2H22011,H20  =  CgH^Oa  +  CeH^Og.     C6H1206  =  2  C8H603. 

Lactose  Dextrose  Galactose  Galactose  Lactic  acid 

This  coagulates  the  casein,  but  when  a  certain  degree  of 
acidity  is  reached  the  ferment  is  killed,  and  the  action  stops. 
This  suggests  the  change  that  takes  place  in  wines  (Chap. 
XXIII),  for  there  also,  as  the  alcohol  increases,  the  ferment 
is  destroyed.  Coagulated  milk  is  frequently  used  to  make  a 
kind  of  cheese  which  undergoes  what  is  known  as  "  butyric 
fermentation,"  producing  an  odor  that  by  some  is  considered 
very  disagreeable. 

After  the  casein  has  been  separated  from  the  milk  by 
means  of  rennet,  the  whey,  which  remains,  may  be  util- 
ized for  making  milk  sugar.  It  is  evaporated  in  a  vacuum 
pan,  purified  by  animal  charcoal,  and  set  aside  to  crystallize 
on  sticks  or  strings  that  are  hung  in  the  vessel.  The  crystals 
have  the  formula  C^H^O^HjO,  and  undergo  lactic  fermenta- 
tion readily,  but  alcoholic  fermentation  with  difficulty. 


MILK  247 

Experiment  135.  Treat  a  sample  of  skim  milk  in  a  test 
tube  with  just  enough  dilute  HC1  to  cause  it  to  coagulate, 
keep  warm  for  some  time,  and  filter.  Burn  a  little  of  the 
"  curd  "  which  remains  on  the  filter,  and  notice,  from  the  odor, 
its  nitrogenous  character.  Neutralize  some  of  the  filtrate 
(the  whey)  with  sodium  hydroxid,  and  test  it  by  Fehling's 
solution  (Experiment  82)  for  milk  sugar. 

The  ash  of  milk  consists  essentially  of  phosphates  and 
chlorids  of  potassium,  sodium,  calcium,  and  magnesium  — 
salts  that  are  especially  needed  for  the  growth  of  bone  ma- 
terial in  the  young.  A  small  quantity  of  citric  acid  is  also 
found  in  milk  in  combination  with  lime. 

STERILIZED   AND   PASTEURIZED    MILK 

Although  milk  which  is  drawn  from  a  healthy,  clean  cow 
by  clean  hands  into  a  bottle  which  has  been  sterilized  is  a 
sterile  fluid,  yet  practically  these  conditions  are  not  attained, 
and  ordinary  milk  contains  a  variety  of  microorganisms. 
Some  of  these  may  produce  souring  and  others  may  be  bearers 
of  disease.  These  organisms  can  be  destroyed  by  a  tempera- 
ture of  100°  C.,  and  a  temperature  of  75°  C.  will  destroy  most 
of  the  pathogenic  bacteria.  This  process  of  heating  is  known 
as  sterilizing,  and  although  it  is  advocated  for  the  treatment 
of  milk  for  infants  and  invalids  especially  in  large  cities, 
yet  the  quality  of  the  milk  is  decidedly  altered. 

Some  of  the  changes  noticed  in  sterilized  milk  are :  — 

1.  A  change  of  taste. 

2.  The  amylolytic  ferment  is  destroyed. 

3.  The  fat  is  not  so  easily  emulsified,  and  so  cannot  be 
so  readily  absorbed  from  the  intestine. 

4  The  casein  does  not  coagulate  so  quickly,  and  there- 
fore is  not  as  digestible. 

5.  The  lactalbumin  is  destroyed. 

On  account  of  these  changes  produced  by  sterilization  the 


248  SANITARY   AND   APPLIED   CHEMISTRY 

method  of  Pasteurization  has  come  into  vogue,  except  in 
those  cases  where  the  milk  must  be  kept  for  several  days. 
Pasteurization  consists  in  keeping  the  milk  at  a  temperature 
of  167°  F.,  for  20  minutes,  instead  of  raising  the  temperature 
to  the  boiling  point,  as  in  sterilizing.  By  this  process  most 
of  the  bacteria  that  are  liable  to  be  present  in  the  milk,  are 
destroyed,  the  taste  of  the  milk  is  not  so  much  altered,  and 
its  nutritive  qualities  are  not  seriously  interfered  with. 
This  milk  will  keep  only  one  or  two  days  under  ordinary 
conditions. 

CONDENSED  AND  EVAPORATED  MILK 

It  is  extremely  convenient  under  some  circumstances 
to  have  at  our  disposal  condensed,  or  evaporated,  milk. 
This  may  be  made  from  "  whole "  milk  or  from  skimmed 
milk,  and  it  may  or  may  not  be  preserved  with  cane  sugar. 
There  is  one  product  on  the  market  which  is  obtained  by 
boiling  the  milk  first  in  open  pans  and  then  in  vacuum 
pans.  This  product  is  served  to  customers  fresh,  and  will 
only  keep  for  a  few  days.  Another  product,  one  which  is 
more  commonly  used  in  the  United  States,  is  canned  milk. 
This  is  made  by  boiling  down  the  milk  in  a  vacuum  pan  and 
mixing  with  cane  sugar  and  sealing  in  the  cans  while  hot. 
This  product  will  keep  for  a  long  time,  but  not  indefinitely, 
as  it  is  liable,  after  a  time,  to  become  ropy  and  unfit  for  use. 

The  unsweetened  variety  is  often  called  "  evaporated  milk  " 
or  "  evaporated  cream."  The  latter,  however,  is  usually  noth- 
ing better  than  whole  milk  evaporated  in  a  vacuum  pan. 

According  to  a  report  of  the  Massachusetts  State  Board  of 
Health,  the  following  is  the  analysis  of  a  normal  condensed 
milk :  total  solids,  74.29%  ;  milk  solids,  32.37%  ;  cane  sugar, 
41.92%  ;  milk  sugar,  11.37%  ;  proteids,  8.46%  ;  fat,  10.65%  ; 
ash,  1.29%  ;  number  of  times  condensed,  2.3. 

United  States  standard  condensed  milk  should  not  contain 


MILK  249 

less  than  28  %  of  milk  solids,  of  which  not  less  than  one 
fourth  is  milk  fat.  Although  it  must  be  admitted  that  in 
some  cases  condensed  milk  can  be  digested  more  readily 
than  fresh  milk,  yet  in  general  its  chief  defect  is  that  it  con- 
tains too  little  fat ;  that  is,  the  dilution  that  is  necessary  on 
account  of  the  large  amount  of  sugar  present,  reduces  the 
per  cent  of  fat  much  below  that  of  normal  milk. 

One  of  the  newest  milk  products  on  the  market  is  "  dried 
milk. "  This  product,  as  well  as  "  dried  cream,"  is  made  by 
feeding  continuously  a  thin  sheet  of  milk  between  two 
steam-heated  cylinders,  revolving  in  opposite  directions, 
and  having  a  surface  temperature  above  100°  C.  The  cyl- 
inders are  slightly  separated,  and  the  milk  is  dried  in  30 
seconds,  and  scraped  from  the  rolls  by  a  knife  edge.  The 
product  is  mixed  with  warm  water  for  use. 

MODIFIED  MILK 

From  an  inspection  of  the  table  given  on  p.  242,  it 
will  be  seen  that  human  milk  differs  from  cow's  milk  in 
several  important  particulars.  The  latter  contains  a  little 
less  fat,  considerably  less  sugar,  more  proteids,  and  more 
ash.  On  this  account  a  great  demand  has  arisen  for  cow's 
milk  so  modified  that  it  shall  approximate  human  milk  in 
composition.  The  general  method  adopted  to  render 
common  milk  better  adapted  to  the  feeding  of  infants  is  to 
bring  the  proteids  and  ash  to  the  right  proportions  by 
dilution  with  water,  then  to  increase  the  per  cent  of  sugar 
by  the  addition  of  lactose,  and  finally  to  add  cream  and 
usually  some  limewater. 

ADULTERATION    OP  MILK 

The  most  common  adulteration  of  milk  is  by  the  addition 
of  water,  but  the  acid  of  milk  is  sometimes  neutralized  by 
the  use  of  baking  soda,  or  various  preservatives  may  be 
added  to  it,  especially  in  warm  weather. 


250  SANITARY   AND   APPLIED   CHEMISTRY 

Experiment  136.  To  detect  sodium  bicarbonate  and  borax 
in  milk,  the  residue  obtained  in  Experiment  134  is  ignited 
to  obtain  the  ash.  After  cooling,  add  a  drop  or  two  of 
HC1,  and  notice  if  there  is  any  effervescence,  which  would 
denote  the  presence  of  carbonates.  Test  this  acidified 
solution  for  borax  by  soaking  in  it,  for  a  short  time,  a  strip 
of  turmeric  paper,  and  allowing  it  to  dry  on  the  side  of  the 
dish  above  the  solution.  If  the  paper  becomes  of  a  dark 
cherry-red  color  when  dry,  and  turns  dark  olive  when 
treated  with  dilute  sodium  hydroxid  solution,  boric  acid  or 
borax  has  been  added  as  a  preservative. 

Experiment  137.  To  test  milk  for  formaldehyde,  use  "  For- 
maldehyde Reagent, "  which  is  made  by  adding  to  a  liter  of 
commercial  hydrochloric  acid  (1.2  specific  gravity)  2  cc. 
of  a  10  %  ferric  chlorid  solution.  Ten  cubic  centimeters  of 
this  reagent  is  added  to  10  cc.  of  milk  in  a  small  porcelain 
casserole,  and  the  solution  is  heated,  slowly,  nearly  to  boil- 
ing, and  at  the  same  time  a  rotary  motion  is  given  to  the 
vessel  to  break  up  the  curd.  When  formaldehyde  is  present 
there  will  appear  a  violet  coloration,  especially  when  it  is 
partially  cooled.  The  color  of  this  solution  will  vary  with 
the  amount  of  formaldehyde  present.  If  this  preservative  is 
absent,  the  solution  slowly  turns  brown.  This  test  is  said  to 
be  delicate  to  „ .  *  .  n  if  the  milk  has  not  soured.  With 

L  o  0  •  U  0  0  %-»- 

sour  milk  the  limit  of  delicacy  is  50*  00.     This  test  cannot 
be  used  when  the  milk  is  flavored  with  vanilla. 

CHEESE 

The  general  method  of  making  cheese  is  by  the  addition 
of  rennet  to  milk  warmed  to  about  41°  C.  Rennet  is  the 
name  given  to  an  infusion  in  brine  of  the  middle  stomach  of 
the  calf.  The  rennet  produces  a  coagulation  of  the  milk  by 
the  action  of  an  enzyme,  which  acts  only  in  an  acid  or  neutral 
solution.  The  coagulated  milk,  after  having  been  broken 


MILK  251 

up  several  times  in  vats  and  heated  to  a  moderate  degree,  is 
inclosed  in  cloth,  and  the  whey  is  pressed  out.  After  the 
cheese  has  become  solid,  the  molds  are  removed  and  the 
cheese  is  placed  in  well-aired  rooms  to  cure.  The  flavor 
improves  with  age,  from  the  development  of  fatty  acids 
and  ethers,  and  by  the  action  of  certain  bacteria.  A 
peptonizing  enzyme  has  been  recently  discovered  in  milk, 
and  to  this  is  probably  due  the  flavors  that  are  induced 
in  cheese  during  the  process  of  ripening.  As  this  process 
goes  on,  the  cheese  is  turned  daily  and  rubbed  with  oil. 
This  improvement  with  age  suggests  what  takes  place  in 
wines  and  liquors  in  the  process  of  aging.  Some  yellow 
coloring  matter,  such  as  "annatto"  or  a  coal  tar  dye,  is 
frequently  added  to  the  cheese  in  the  process  of  manufac- 
ture. Cheeses  are  generally  classified  as  cream  cheese, 
whole  cheese,  and  skim-milk  cheeses. 

Soft  cheeses,  like  Brie,  Neufchatel,  and  Cammembert,  are 
made  in  a  short  time,  and  by  coagulating  with  rennet  at  a 
low  temperature ;  i.e.  below  30°  C. 

Medium  cheeses  are  allowed  to  drain  for  some  time 
without  pressure.  The  English  "Stilton"  and  the  Swiss 
"Gruyere"  belong  to  this  class. 

Hard  cheeses,  like  "Cheddar,"  and  the  common  cheese 
of  the  United  States,  is  made  by  coagulating  at  a  higher 
temperature  —  30°  to  35°  —  and  then  thoroughly  pressing. 

The  names  applied  to  cheeses  are  frequently  those  of  the 
locality  from  which  they  originally  came.  Limburger  is.  a 
soft,  fat  cheese.  Roquefort  is  made  from  the  milk  of  the 
ewe.  Parmesan  is  a  dry  Italian  cheese,  with  a  very  large 
amount  of  casein,  and  a  moderate  percentage  of  fat.  Edam  is 
a  Dutch  cheese,  quite  dry,  and  having  a  red  coloring  on  the 
outside.  The  following  compilation  by  Woll1  shows  the 
average  composition  of  some  common  varieties  of  cheese. 
1  Dairy  Calendar,  p.  223. 


252 


SANITARY    AND    APPLIED    CHEMISTRY 


WATER 

CASEIN 

FAT 

SUGAR 

ASH 

Cheddar    

34.38 

26.38 

32.71 

2.95 

3.68 

Cheshire    

32.59 

32.51 

26.06 

4.53 

431 

Stilton       

30.35 

28.85 

35.39 

1.59 

3.83 

Brie       

50.35 

17.18 

25.12 

1.94 

5.41 

Neufchatel      

44.47 

14.60 

33.70 

4.24 

2.99 

Roquefort       ...              . 

31.20 

27.63 

33.16 

2  00 

6.01 

Edam    

36.28 

24.06 

30.26 

4  60 

4.90 

Swiss    

35.80 

24.44 

37.40 

2.36 

Full  cream  (  average  )      ... 

38.60 

25.35 

30.25 

2.03 

4.07 

It  is  evident  that  cheese  is  made  up  of  about  one  third 
water,  one  third  nitrogenous  matter,  and  one  fourth  fat.  The 
mineral  matter  is  also  of  considerable  importance. 

Cheese  is  so  rich  in  nitrogenous  matter,  and  also  in  fat, 
that  it  might  properly  form  a  valuable  food  for  the  poorer 
classes,  while  it  is  used  by  the  more  wealthy  as  a  relish.  A 
comparison  with  other  animal  foods  shows  very  distinctly  its 
theoretical  value  as  food.  It  is  rather  difficult  to  digest 
in  the  stomach,  unless  finely  grated  or  dissolved,  as  the  fat 
protects  the  casein  from  the  action  of  the  digestive  fluids. 
Protein  and  fat  are  often  much  cheaper  in  cheese  than  in 
meat. 

Kich  cheese  is  very  liable  to  decay,  for  it  furnishes  an 
excellent  medium  for  the  growth  of  living  organisms.  In  1884 
Dr.  V.  C.  Vaughan  isolated  from  cheese  the  poison,  which 
he  called  tyrotoxicon.  This  poison,  which  produces  gastro- 
intestinal irritation  and  nausea,  is  developed  in  milk,  ice 
cream,  and  cheese  when  the  material  is  stored  in  dark,  damp, 
filthy  rooms  or  cellars,  or  where  vessels  used  for  holding 
the  milk  are  not  thoroughly  cleaned  for  use.  With  proper 
care  of  the  milk  there  is  no  danger  of  the  development  of 
this  poison. 


MILK  253 

About  the  only  falsification  of  cheese,  aside  from  the 
fraudulent  sale  of  skim-milk  cheese  for  fall-cream  cheese, 
is  the  so-called  "  filled  cheese,"  which  is  made  by  working 
into  the  material  in  the  process  of  manufacture  some  foreign 
fat,  as  oleo  or  lard. 

BUTTER  AND  BUTTER  SUBSTITUTES 

Commercial  butter  is  somewhat  granular  in  appearance, 
and  this  is  considered  a  very  valuable  quality  of  butter.  It 
has  a  fragrant  odor  and  an  agreeable  taste.  It  contains 
more  or  less  casein,  which  causes  it  to  undergo  decompo- 
sition, if  the  butter  has  not  been  thoroughly  washed.  Butter 
must  be  salted  in  order  to  preserve  it  for  any  length  of 
time.  The  composition  of  butter  fat  has  been  noted  under 
the  discussion  of  milk.  The  proportion  of  these  different 
fats  varies  within  slight  limits  only,  and  on  this  account 
it  is  not  difficult  to  distinguish  between  natural  butter  and 
oleomargarin,  or  a  butter  that  has  been  adulterated  with 
other  fats.  Cream  which  is  obtained  by  the  use  of  the 
separator  should  be  allowed  to  ripen  for  some  time  before 
it  is  churned  into  butter.  In  this  process  of  ripening, 
certain  bacteria  take  an  active  part,  and  to  such  a  degree  is 
this  the  case  that  the  variety  of  bacteria  in  the  dairy  affect 
very  materially  the  quality  of  the  butter.  Indeed  it  has 
become  the  custom  in  some  dairies  to  import  bacteria,  or 
some  material  containing  bacteria  of  a  specially  high  grade, 
so  as  to  make  a  fine  quality  of  "  June  butter." 

On  the  continent  of  Europe  the  people  purchase  butter 
every  day  for  that  day's  supply  only,  as  the  butter  is  never 
salted,  and  as  it  usually  contains  considerable  buttermilk 
it  will  not  keep.  Butter  has  the  average  composition: 
water,  13.59%;  fat,  84.39%;  casein,  .74%;  milk,  .50%; 
lactic  acid,  .12  %;  and  salts,  .66  %. 


254  SANITARY   AND   APPLIED   CHEMISTRY 

"Renovated,"  or  "Process,"  butter  is, in  general,  made  as 
follows:  Old,  rancid,  and  unsalable  butter  is  melted  in  a 
large  tank,  surrounded  by  a  hot-water  jacket,  at  a  temper- 
ature of  about  45°  C.  The  curd  and  brine  are  then  drawn 
off  at  the  bottom  and  the  scum  is  taken  off  from  the  top. 
Air  is  blown  through  the  mass,  to  remove  the  disagreeable 
odor,  and,  after  mixing  with  some  milk,  the  mass  is  churned, 
and  then  run  into  ice-cold  water  so  as  to  make  it  granular 
in  structure.  The  butter  is  then  ripened,  worked  to  free  it 
from  buttermilk,  and  salted.  Some  states  require  that  this 
should  be  marked  "  Renovated  Butter  "  when  exposed  for 
sale,  while  others  allow  dealers  to  handle  this  product  with- 
out restriction. 

The  manufacture  of  artificial  butter,  butterine,  or  oleo- 
margarin  has  received  encouragement,  both  in  the  United 
States  and  abroad,  on  account  of  the  low  cost,  and  also 
because  the  imitations  are  frequently  better  and  more  pala- 
table than  low  grades  of  cheap  butter.  The  materials  used 
in  the  manufacture  of  artificial  butter  are :  "  neutral "  or 
leaf  lard,  from  25  to  60%  ;  oleo  oil,  from  20  to  50%  :  some 
vegetable  oil,  like  cottonseed  oil,  from  5  to  25%  ;  milk  or 
cream,  from  10  to  20%;  butter,  from  2  to  10  or  12%  ;  salt 
and  annatto  or  aniline  coloring  matter.  For  different  grades 
of  oleomargarin  different  quanties  of  these  substances  are 
used. 

"  Neutral "  is  made  by  melting  leaf  lard,  and  allowing  it 
to  "  grain  "  by  letting  it  stand  at  a  temperature  favorable 
for  the  separation  of  the  stearin  in  coarse  grains.  Oleo  oil 
is  made  in  immense  quantities,  both  for  use  in  the  manu- 
facture of  butterine  in  the  United  States,  and  for  shipment 
abroad.  The  process  of  manufacture  is  to  cut  the  beef  fat 
into  small  pieces  and  "  render"  it  in  water-jacketed  kettles  at 
the  lowest  possible  temperature  that  is  practical.  The  scum 
which  separates  at  the  top  is  drawn  off  and  the  scraps  settle 


MILK  255 

to  the  bottom.  The  liquid  fat  is  then  run  into  vats,  where 
it  becomes  partially  cool.  The  semiliquid  mass  is  wrapped 
up  in  cloths  and  pressed  to  remove  the  liquid  oil  from  the 
solid  fat.  The  solid  fat,  known  as  oleo-stearin,  is  used  in 
the  tanning  and  leather  trades,  by  candle  makers,  for  the 
manufacture  of  soap  and  of  "  compound  "  lard.  The  oleo 
oil  is  used  in  the  manufacture  of  oleomargarin. 

For  the  manufacture  of  oleomargarin  certain  proportions 
of  the  ingredients,  mentioned  above,  are  churned  and  run 
into  ice  water  to  cool  the  mass  rapidly,  and  then  worked 
like  ordinary  butter.  The  particular  variety  made  depends 
upon  the  market.  The  manufacturers  exercise  great  care 
that  the  process  shall  be  a  clean  one,  and  most  authorities 
agree  that  a  good  quality  of  butterine  is  better  than  a  bad 
quality  of  butter. 

At  the  instance  of  the  dairy  interests  of  the  United  States, 
however,  a  tax  probably  intended  to  be  prohibitory  has  been 
levied  upon  butterine.  This  tax  is  very  small,  1  cent  per 
pound  in  case  the  butterine  is  not  colored.  If  it  is  colored  in 
imitation  of  butter,  the  tax  is  10  cents.  Until  this  law  was 
passed  at  a  recent  session  of  Congress,  the  manufacture  of 
butterine  constantly  increased,  even  though  the  industry 
was  obliged  to  bear  a  small  tax.  In  1903  the  total  product 
of  oleomargarin  was  but  71,237,438  Ibs.,  while  the  previous 
year  it  was  123,133,852  Ibs. 

Experiment  138.  Place  about  5  grams  of  butter  in  a  small 
flask,  add  to  it  30  cc.  of  a  solution  of  potassium  hydroxid 
in  alcohol,  and  warm  on  a  water  bath.  After  the  soap  has 
had  time  to  form,  and  while  some  alcohol  still  remains,  add 
about  30  cc.  of  dilute  sulfuric  acid,  and  warm,  the  solution. 
Notice  the  peculiar  odor  of  butyric  ether,  especially  if  the 
solution  is  allowed  to  stand. 

Experiment  139.  Foam  test  for  purity  of  butter.  Heat 
about  3  grams  of  the  sample  in  a  large  iron  spoon  over  a  low 


256  SANITARY   AND   APPLIED   CHEMISTRY 

Bunsen  flame,  stirring  constantly.  Genuine  butter  will 
boil  quietly,  with  the  production  of  considerable  froth  or 
foain,  which  may,  on  removal  from  the  flame,  boil  up  over  the 
side  of  the  spoon.  Renovated  butter  or  oleomargarin  will 
sputter  and  act  like  hot  fat  containing  water,  but  will  not 
foam.  Examine  also  the  curdy  particles  when  the  sample 
is  removed  from  the  flame;  in  the  case  of  genuine  butter 
these  particles  are  small  and  finely  divided,  but  in  the  case 
of  oleomargarin  the  curd  will  gather  in  large  masses. 

Experiment  139  a.  To  make  the  "  milk  "  test  for  butter, 
place  about  60  cc.  of  sweet  milk  in  a  wide-mouthed  bottle, 
which  is  set  in  a  vessel  of  boiling  water.  When  the  milk 
is  thoroughly  heated,  a  spoonful  of  the  butter  is  added  and 
the  mixture  is  stirred  until  the  fat  is  melted.  The  bottle  is 
then  placed  in  a  dish  of  ice  water,  and  the  stirring  con- 
tinued until  the  fat  solidifies.  If  the  sample  is  butter,  either 
fresh  or  renovated,  it  will  be  solidified  in  a  granular  con- 
dition and  distributed  through  the  milk  in  small  particles. 
If,  on  the  other  hand,  the  sample  consi&fe  of  oleomargarin, 
it  solidifies  practically  in  one  piece,  so  that  it  may  be  lifted 
by  the  stirrer  from  the  milk. 

By  the  two  tests  just  described,  the  first  of  which 
distinguishes  fresh  butter  from  process  or  renovated  butter 
and  oleomargarin,  and  the  second  of  which  distinguishes 
oleomargarin  from  either  fresh  butter  or  renovated  butter, 
the  nature  of  the  sample  examined  may  be  determined.1 

Experiment  140.  To  test  for  coal  tar  colors  in  butter,  a 
small  sample  is  mixed  on  a  porcelain  plate  with  Fuller's 
earth,  and  if  they  are  present,  there  will  be  a  red  mass, 
while  if  absent  the  color  will  be  only  light  yellow  or 
brown. 

i  Bigelow  and  Howard,  U.  S.  Dept.  Agric.,  Bu.  Chem.,  Bui.  100,  p.  51. 


CHAPTER  XXII 

BEVERAGES 

THE  ordinary  beverages,  not  including  milk,  may  be 
classified  as  nonalcoholic  and  alcoholic. 

NONALCOHOLIC    BEVERAGES 

From  the  earliest  time  there  has  been  a  demand  for  some 
slightly  stimulating  beverage  that  is  nonintoxicating  in 
character.  The  simple  herb  drinks,  such  as  catnip  tea, 
sage  tea,  sassafras  tea,  etc.,  have  been  used  and  are  more 
agreeable  than  hot  water  alone,  which  in  itself  is  slightly 
stimulating.  It  is  interesting  to  observe  that  in  the  very 
early  history  of  the  world,  people,  in  different  countries  and 
under  different  conditions,  selected  certain  plants  which 
seemed  to  be  stimulating  in  their  effects,  and  made  bever- 
ages from  them.  It  was  later  found  out  that  the  plants 
so  selected  contain  certain  active  principles  which  were 
stimulating  in  character. 

The  most  important  of  the  beverages  at  present  in  use  are 
tea,  coffee,  and  cocoa.  There  is  a  growing  demand  for  tea 
in  the  United  States.  The  imports  of  tea  for  1905  were 
96,779,145  Ibs.,  valued  at  $15,003,588.  The  importation  of 
coffee  in  1905  amounted  to  893,889,352  Ibs.,  valued  at 
$75,307,536.  The  importation  of  cocoa  (crude)  for  1905 
amounted  to  79,722,791  Ibs.,  valued  at  $8,965,387,  besides 
923,127  Ibs.  of  manufactured  cocoa  products.1  The  per 
capita  consumption  of  these  beverages  in  1903  is  reported, 

1  Bui.  Dept.  Com.  and  Labor.     Dec.  1905. 
8  257 


258  SANITARY   AND   APPLIED   CHEMISTRY 

for  tea  1.30  Ibs.,  for  coffee  10.79  Ibs.  In  Great  Britain  the 
per  capita  consumption  of  tea  is  four  times  that  of  the 
United  States,  while  the  per  capita  consumption  of  coffee  is 
only  one  tenth  that  of  the  United  States. 

TEA 

About  51%  of  our  tea  comes  from  China  and  42%  from 
Japan.  The  history  of  the  discovery  of  tea  is  lost  in  antiq- 
uity. The  first  authentic  account  was  as  late  as  350  A.D., 
while  in  European  literature  the  earliest  record  appears  in 
1550.  The  first  consignment  of  tea  into  England  took  place 
in  1657,  and  it  came  into  the  United  States  in  1711.  Genu- 
ine tea  is  prepared  from  the  leaf  of  the  Thea  sinensis,  a 
plant  which  grows  to  the  height  of  4  to  5  ft.  The  leaves 
are  ready  for  picking  at  the  end  of  the  third  year,  and  the 
average  life  of  the  plant  is  about  10  yr.  The  leaves  are 
picked  at  least  three  times  per  year,  —  in  April,  May,  and 
the  middle  of  July.  The  first  pickings  are  the  best  and 
tenderest,  and  make  the  best  grade  of  tea. 

PREPARATION    OF   THE   TEA 

After  sorting,  the  natural  moisture  is  partially  removed 
by  pressing  and  rolling,  then  the  leaves  are  dried  by  gently 
roasting  in  an  iron  pan  for  a  few  moments.  They  are  then 
rolled  on  bamboo  tables  and  again  roasted,  and  finally  sepa- 
rated into  the  various  grades  by  passing  through  sieves. 

The  difference  between  green  and  black  tea  is  mainly 
due  to  the  fact  that  the  green  is  steamed  thoroughly  and 
then  rolled  and  carefully  fired,  whereas  black  tea  is  first 
made  up  into  heaps  which  are  exposed  to  the  air  and  al- 
lowed to  ferment,  and  thus  the  olive-green  is  changed  into 
a  black  color. 

In  the  preparation  of  Japan  tea,  the  leaves  are  steamed 
in  a  tray  over  boiling  water.  They  are  then  heated  on  a 
tough  paper  membrane  over  an  oven  and  at  the  same  time 


BEVERAGES  259 

stirred  with  the  hand.  The  tea  after  being  thus  fired 
is  dried  for  some  hours  and  sorted  by  passing  through 
sieves.  Then  it  is  sent  to  the  warehouse,  where  sometimes 
the  "  facing  process "  is  carried  on,  by  heating  the  tea  in 
large  bowls  and  adding  various  pigments  to  it. 

There  are  but  few  spurious  teas  on  the  market,  but  the 
range  in  quality  is  very  great.  On  account  of  the  strict 
enforcement  in  the  United  States  of  the  adulteration  act, 
no  adulterated  tea  is  permitted  to  be  imported,  and  the  con- 
sumer is  reasonably  well  protected.  He  usually  secures 
genuine  leaves  though  he  may  get  very  inferior  grades  of  tea. 

Tea,  as  prepared  for  the  foreign  market,  is  exposed  to  a 
large  number  of  sophistications  and  adulterations,  mainly 
for  giving  it  an  increased  weight.  These  adulterations 
include  adding  foreign  leaves,  spent  tea  leaves,  metallic 
iron,  sand,  brick  dust,  etc. 

Again,  substances,  such  as  catechu  or  similar  materials 
that  contain  tannin,  are  added  to  produce  an  artificial 
appearance  of  strength.  Another  sophistication,  which  is 
practiced  especially  on  green  tea,  consists  in  imparting  a 
bright  appearance  to  inferior  tea  by  means  of  coloring  mat- 
ter or  facing ;  for  this  purpose  they  use  soapstone,  gypsum, 
Prussian  blue,  indigo,  turmeric,  and  graphite.  Another 
form  of  sophistication  is  practiced  on  exhausted  tea  leaves 
by  a  similar  process  of  facing.  It  is  even  said  to  be  possi- 
ble, by  careful  manipulation,  to  change  black  tea  to  green 
and  vice  versa. 

The  Indian  teas  are  very  much  stronger  than  those  from 
China  and  Japan,  so  that  they  produce  a  beverage  that  seems 
too  strong  to  those  accustomed  to  Chinese  and  Japanese  teas. 
The  Indian  teas  only  come  in  contact  with  the  hands  of  the 
workmen  at  the  time  of  picking.  The  Chinese  teas  are 
manufactured  almost  entirely  by  hand,  although  sometimes 
the  feet  are  used  in  rolling  the  cheaper  grades. 


260 


SANITARY   AND   APPLIED   CHEMISTRY 


A  substance  called  "  lye  tea  "  is  frequently  put  upon  the 
foreign  market.  This  consists  of  fragments  of  genuine  leaves, 
foreign  leaves,  and  mineral  matter  held  together  by  a  starch 
solution  and  colored  with  various  preparations.  It  is  prob- 
able that  the  addition  of  foreign  leaves  is  but  little 
practiced  at  the  present  time  in  the  United  States. 

In  England  black  teas  are  used  much  more  than  the 
green.  This  is  due  to  the  supposition  that  black  teas  con- 
tain less  astringent  matter  and  also  act  less  upon  the  nerves. 
By  comparison  of  analysis  of  black  and  green  tea  it  is  evi- 
dent that  there  is  less  material  soluble  in  hot  water  in  the 
former.1 


GREEN  TEA 

BLACK  TEA 

Crude  protein     .... 
Fiber     

37.43 
10.06 

38.90 
10.07 

Ash  

4.92 

4.93 

Thein     

3.20 

3.30 

Tannin       

10.64 

4.89 

Total  nitrogen     .... 

6.99 

6.22 

The  important  constituents  are  the  extract,  a  certain 
amount  of  tannin  and  thein,  and  the  volatile  oil.  On  account 
of  the  presence  of  a  large  amount  of  tannin  in  tea,  which  is 
extracted  by  heating  with  water,  it  is  important,  in  making 
the  beverage,  that  the  water  should  not  stand  for  any 
length  of  time  upon  the  leaves.  On  this  account  a  much 
more  wholesome  beverage  may  be  made  by  the  use  of  the 
tea-ball  with  the  hot  water.  It  is  a  great  mistake  to  allow 
the  tea  to  draw,  as  the  saying  is,  for  hours  at  a  time. 
Freshly  boiled  water  should  be  used  in  making  tea,  and 
it  should  be  thoroughly  boiling  when  poured  upon  the 
leaves,  and  allowed  to  digest  about  three  minutes,  not 
1  Analysis  by  Kozai :  W.  G.  Thompson,  "Practical  Dietetics,"  p.  211. 


BEVERAGES  261 

longer.  Longer  infusion  will  make  the  tea  appear  stronger 
but  will  spoil  its  delicate  flavor,  and  extract  too  much  tannin, 
which  will  have  an  injurious  effect  on  the  system.  The 
water  used  should  not  be  too  soft,  as  that  will  extract 
more  soluble  material,  nor  should  it  be  extremely  hard. 
The  thein  is  practically  all  extracted  from  tea  within  the 
first  five  minutes,  while  the  amount  of  tannin  continues 
to  increase  for  40  minutes  or  more.  The  infusion  should 
be  poured  off  from  the  grounds  as  soon  as  made. 

According  to  Hutchison  an  ordinary  cup  of  tea  will  con- 
tain nearly  a  grain  of  thein,  and  from  1  to  4  grains  of 
tannin,  dependent  on  the  kind  of  tea  used.  There  is  no 
direct  relation  between  the  quality  or  price  of  the  tea  and 
the  proportion  of  thein.  This  substance,  thein,  which  has 
the  formula  C8H10N402 ,  is  an  ureide  belonging  to  the  same 
general  class  as  guaranin,  xanthin,  uric  acid,  etc.  The  vola- 
tile oil  which  is  present  gives  to  the  tea  its  agreeable  flavor 
and  aroma. 

Experiment  141.     Make  a  decoction  of  tea  in  a  test  tube, 
pour  it  off  from  the  grounds,  and  test  a  part  for  tannic  acid. 
First,  by  ferric  chlorid ; 
Second,  ferrous  sulf ate ; 
Third,  by  a  mixture  of  the  two  reagents. 
A  black  or  bluish  black  color  (ink)  will  be  produced. 

PARAGUAY   TEA 

There  is  another  variety  of  tea  known  as  Paraguay  tea, 
or  Yerba  Mate,  which  was  selected  by  the  people  of  South 
America  to  use  as  a  beverage.  This  tree  grows  wild,  and  is 
known  to  the  botanist  as  Ilex  paraguayensis.  The  tea 
is  prepared  in  Paraguay  by  cutting  off  the  small  twigs  and 
leaves  and  placing  them  on  a  clean  plot  of  earth  surrounded 
by  fire.  In  this  way  the  leaves  are  wilted  and  cured,  and 
they  are  afterward  dried  on  a  grating  over  a  fire,  and  then 


262  SANITARY   AND   APPLIED   CHEMISTRY 

reduced  to  a  coarse  powder.  The  infusion,  which  is  pre- 
pared in  a  kind  of  gourd,  is  conveyed  to  the  mouth  by 
means  of  a  reed  or  a  silver  tube  called  a  "bombilla,"  with 
a  strainer  at  the  end. 

Mate'  contains  1.3%  of  thein  and  16%  of  tannic  acid,  also 
an  aromatic  oil  and  gluten.  The  tannic  acid  has  entirely 
different  properties  from  that  contained  in  tea  or  coffee. 

COFFEE    LEAF    TEA 

In  some  coffee-growing  countries  the  natives  use  the 
leaves  of  the  coffee  tree  to  make  an  infusion  which  has  about 
the  same  constituents  and  properties  as  ordinary  tea. 

COFFEE 

Coffee  is  the  seed  of  the  Coffea  arabica,  indigenous  in 
Abyssinia  and  Arabia,  and  this  plant,  at  the  present  time,  is 
grown  in  Java,  the  West  Indies,  in  Ceylon,  Mexico,  and 
Central  and  South  America.  It  was  used  in  the  remotest 
time  in  Arabia.  It  was  introduced  into  Constantinople  in 
1574;  in  1660  it  was  carried  from  Mocha  to  Java,  and 
thence  specimens  of  the  tree  were  taken  to  Holland  and 
France.  Coffeehouses  were  opened  in  London  about  the 
middle  of  the  seventeenth  century.  In  1809  the  first  cargo 
was  shipped  to  the  United  States.  There  is  a  great  difference 
in  the  quality  and  flavor  of  coffee  from  different  localities. 

The  coffee  tree  is  productive  for  about  thirty  years.  The 
trees  are  usually  planted  every  twenty  years  and  grow 
best  on  the  uplands.  The  trees  are  raised  from  seeds 
in  nurseries  and  transferred  to  the  plantations.  In  Java 
the  picking  of  the  berry  begins  in  January,  and  lasts 
three  or  four  months ;  in  Brazil,  the  picking  begins  in  April 
and  May,  and  continues  throughout  the  season.  After 
the  berries  are  harvested,  the  first  operation  by  which  they 
are  treated  is  called  pulping.  Sometimes  the  berries  are 


BEVERAGES 


263 


pulped  in  the  soft  state,  sometimes  they  are  first  dried,  and 
then  the  dried  skins  are  removed  by  a  machine  called  a 
huller.  The  West  India  and  Brazilian  method  is  to  macer- 
ate the  berries  in  a  large  vat,  where  they  are  treated 
by  what  is  known  as  a  pulping  machine,  which  is  an  iron 
cylinder  set  with  teeth,  which  removes  the  outer  covering. 
The  loosened  pulp  is  carried  out  at  one  side  and  the  berries 
sink  to  the  bottom  of  the  vat.  The  berries  are  afterward 
dried,  cleaned,  and  sorted. 

The  next  process  is  the  roasting  of  the  bean.  This  may 
be  carried  on  directly  over  a  fire  or  in  an  oven.  The  average 
loss  of  weight  in  the  process  of  roasting  is  about  16%. 
This  process  develops  an  essential  oil  and  brings  out  the 
aroma  of  the  coffee.  If  the  operation  is  carried  too  far, 
the  best  properties  and  ingredients  are  lost. 

The  following  analysis  by  Konig  shows  the  difference  be- 
tween raw  and  roasted  coffee :  — 


RAW 

COFFEE 

BOASTED 
COFFEE 

Water    .    . 

11.23 

1.15 

Caffein   

1.21 

1.24 

Fat    

12.27 

14.48 

Sugar     

855 

66 

Cellulose    

18.17 

10.89 

Nitrogenous  substance     

12.07 

13.98 

Other  non-nitrogenous  matter  

32.58 

45.09 

Ash    

3.92 

4.76 

The  effect  of  roasting  is  to  drive  off  a  large  part  of  the 
water,  and  to  caramelize  most  of  the  sugar.  The  bean 
becomes  more  brittle,  and  the  caffeol1  (C8H1002),  to  which 
coffee  largely  owes  its  odor  and  flavor,  is,  at  the  same  time, 

1  Hutchison,  "Food  and  Dietetics,"  p.  310. 


264  SANITARY   AND   APPLIED   CHEMISTRY 

developed.  The  active  principle,  called  thein,  or  caffein 
(  CgHj^Oa),  is  believed  to  be  identical  with  that  of  tea.  The 
infusion  of  coffee  also  contains  some  nitrogenous  material. 

Ground  coffee  is  especially  liable  to  be  adulterated. 
Some  of  the  chief  substances  added  to  the  commercial  ground 
coffee  are  chicory,  caramel,  peas,  and  roasted  grains,  such  as 
corn,  wheat,  and  rye.  There  has  also  been  found  upon  the 
market  an  artificial  coffee  bean  which  contains  absolutely  no 
coffee,  and  is  made  by  compression  of  harmless,  starchy  ingre- 
dients into  the  form  of  the  coffee  bean.  This  is  mixed  with 
the  genuine  beans.  The  raw  coffee  bean  is  sometimes  sub- 
jected to  the  process  of  sweating,  by  which  it  is  increased 
in  size  and  improved  in  color  and  flavor ;  it  is  sometimes 
moistened  with  water  containing  a  little  gum  and  colored 
with  various  pigments,  such  as  Prussian  blue  and  turmeric, 
so  as  to  improve  its  appearance.  In  this  way,  for  instance, 
Mexican  coffee  is  made  to  resemble  Java  coffee. 

In  regard  to  making  the  beverage  coffee,  there  are  two 
methods,  either  of  which  may  be  used.  The  first  is  to  put 
ground  coffee  into  cold  water  and  bring  the  decoction  to  the 
boiling  point.  The  second,  and  probably  better,  method  is  to 
have  the  water  boiling  tumultuously  and  add  to  it  the  required 
amount  of  finely  ground  coffee,  boil  not  more  than  three 
minutes,  and  then  serve  immediately.  If  the  coffee  is 
allowed  to  boil  for  any  length  of  time,  not  only  is  the  tannin 
extracted  from  the  berry,  but  the  agreeable  aroma  and 
flavor  is  lost,  as  it  is  carried  off  with  the  volatile  oil.  The 
coffee  is  then  not  as  wholesome,  and  it  certainly  is  not  as 
agreeable  in  flavor. 

Many  persons  find  that  black  coffee  produces  less  ill-effects 
upon  the  system  than  does  coffee  served  with  cream.  This 
may  be  due  to  the  compound  produced  by  the  action  of  the 
tannin  of  the  coffee  upon  the  proteid  substances  of  the  milk. 
Ga.fi  au  lait,  which  is  a  mixture  of  three  parts  of  hot  milk 


BEVERAGES  265 

with  one  part  of  coffee,  is  a  popular  beverage  in  many 
countries.  It  will  be  noticed  that  coffee  contains  less  of 
the  alkaloid  than  tea. 

There  are  many  varieties  of  coffee  upon  the  market,  but 
the  Mocha  and  Java  coffees  usually  command  the  highest 
price.  The  low  grades  of  coffee  have  decreased  very  much 
in  price  during  the  last  few  years.  This  is  probably  due 
to  the  competition,  and,  also,  to  the  fact  that  immense  quan- 
tities of  the  cheaper  grades  are  raised  in  South  and  Central 
America.  The  latest  official  report  (1905)  shows  that  three 
fourths  of  the  coffee  imported  into  the  United  States  comes 
from  Brazil.  The  coffees  range  in  price  from  8  cents  to  45 
cents  per  pound  at  retail.  Some  persons  have  become  accus- 
tomed to  the  strong  black  coffee  made  from  the  Bio  brand, 
and  to  meet  their  demand,  in  "  blending,"  some  Bio  is  often 
added  to  other  grades. 

There  is  no  great  objection  to  the  substitutes  for  coffee 
that  are  upon  the  market,  if  they  are  not  bought  as  coffee. 
Many  of  these  are  no  doubt  wholesome  enough,  and  if 
coffee  has  been  found  to  disagree  with  the  system,  it  is 
probably  better  to  use  some  beverage  of  this  kind,  which 
is  simply  an  extract  of  a  roasted  cereal. 

COCOA   AND   CHOCOLATE 

The  raw  material  from  which  cocoa,  and  chocolate  is  made, 
is  the  seed  of  the  TJieobroma  cacao.  It  grows  most  readily 
from  Mexico  to  Peru  on  the  west  coast  of  the  American 
continent,  in  Mexico  and  Brazil  on  the  east  coast,  and  in 
the  West  India  Islands.  It  was  introduced  into  Europe  by 
the  Spaniards  in  1519.  Chocolate  was  first  prepared  in  the 
United  States  in  1771,  at  Danvers,  Mass.1  The  tree  is  about 
18  or  20  ft.  high,  blooms  continuously,  and  yields  two  crops 
a  year.  The  lemon-yellow  fleshy  fruit  is  about  7  in.  long, 
1  Harrington,  "  Practical  Hygiene,"  p.  174. 


1200 


SANITARY   AND   APPLIED   CHEMISTRY 


something  like  a  short  cucumber  in  appearance,  and  has  ten 
longitudinal  ridges.  The  seeds  are  arranged  in  five  rows 
in  the  pulpy  flesh.  There  are  two  processes  for  preparing 
the  seed  for  the  market.  For  unfermented  cocoa  the  seeds 
are  separated  from  the  pulp  and  dried  in  the  sun ;  for  the 
fermented  cocoa  the  seeds  are  placed  in  piles  and  allowed 
to  ferment,  before  being  dried.  Much  of  the  acridity  and 
bitterness  disappears  in  this  process  of  fermentation.  The 
principal  operations  in  the  process  of  manufacture  are,  first, 
the  sifting  of  the  raw  cocoa  to  remove  the  sand  and  dust ; 
second,  the  separation  by  hand  of  the  larger  stones  and  empty 
pods,  etc.  ;  third,  roasting  the  cleaned  seeds. 

The  following  table l  shows  the  composition  of  some  cocoa 
products :  — 


PURE  PLAIN 
CHOCOLATE, 
AVERAGE  or 
6  ANALYSES 

PURE  SWEET 
CHOOOLATE, 
AVERAGE  or 
12  ANALYSES 

PURE  COCOA, 
AVERAGE  or 
26  ANALYSES 

COCOA  SHELLS 
(HANDSHELLBD), 
AVERAGE  or 
17  ANALYSES 

Water  

3.78 

2.17 

6.23 

4.87 

Ash  

3.15 

1.40 

6.49 

10.43 

Theobromiu  

.78 

.35 

1.15 

.49 

Caffein      

.13 

.08 

.16 

.16 

Other  nitrogenous  substances 
(protein)    

12.36 

4.58 

18.34 

14.46 

Crude  fiber    

2.86 

.95 

4.48 

16.66 

Sugar    

56.44 

Pure  starch     

18.11 

2.88 

11.14 

4.13 

Other  nitrogen-free  substances 
Fat   

16.64 
62.19 

7.64 
23.51 

26.32 
26.69 

46.16 
2.76 

Cocoa  is  not  only  used  to  make  a  pleasant  and  exhilarat- 
ing beverage;  it  is  a  valuable  food  material.     The   most 

1  Rep.  Conn.  Agric.  Exp.  Station,  1903,  Pt.  IT,  p.  125. 


BEVERAGES  267 

important  constituents  are  fat,  theobromin,  which  is  the 
alkaloid  or,  properly  speaking,  the  ureide  of  cocoa,  a  little 
starch,  and  some  albumin  and  fibrin.  The  fat  usually  forms 
about  50  %  of  the  husk  and  bean.  It  is  a  mixture  of  the 
glycerides  of  stearic,  palmitic,  lauric,  and  arachidic  acids, 
and  is  extensively  used  in  pharmacy  under  the  name  of 
"  cocoa  butter  "  Theobromin,  which  was  discovered  in  1841 
by  Woskresensky,  is  very  closely  related  to  xanthine,  being 
dimethyl  xanthine,  C5H2(CH3)2N4Oy  Caffein  is  trimethyl 
xanthine,  C5H(CH3)3N402. 

The  commercial  preparations  of  cocoa  are  quite  numerous. 
Plain  chocolate  is  prepared  by  grinding  roasted  and  husked 
seeds  to  a  paste  and  pressing  in  the  form  of  cakes.  When 
this  is  combined  with  sugar,  vanilla,  etc.,  sweet  chocolate  is 
the  product.  Since  there  is  so  much  fat  in  the  cacao,  this  is 
frequently  partially  removed,  and  the  residue  is  put  on  the 
market  under  the  name  of  cocoa.  Cocoa  shells  or  husks  are 
sometimes  used  for  making  an  exceedingly  weak  beverage  of 
this  class,  which  contains  little  fat,  but  considerable  nitrog- 
enous matter  and  extractives.  Cocoa  "nibbs"  are  the 
bruised,  roasted  seeds  freed  from  the  hardened  grains,  and 
contain  all  the  fat.  The  names  that  are  applied  to  the  differ- 
ent preparations  of  cocoa  and  chocolate  vary  in  different 
countries.  Cocoa  and  chocolate  preparations  are  very  readily 
adulterated,  but,  after  all,  the  general  adulterants,  if  such 
they  may  be  called,  are  sugar  and  starch,  which  are  not 
injurious,  but  only  decrease  the  cost  for  the  benefit  of  the 
manufacturer.  The  genuine  chocolate  should  contain  all 
the  original  fat.  An  inferior  vanilla  chocolate  is  flavored 
with  the  artificial  vanillin  and  coumarin  in  place  of  the 
finer  flavored  vanilla  bean. 

It  is  said  that  the  term  "  soluble  cocoa "  is  erroneous,  as 
very  little  of  the  albuminous  substances  or  the  fat  are  solu- 
ble. In  order  to  grind  the  bean  to  a  very  fine  powder  it 


268  SANITARY   AND  APPLIED  CHEMISTRY 

must  be  mixed  with  sugar  or  starch,  and  this,  in  fact,  is  the 
method  used  in  the  preparation  of  some  of  the  powders  rec- 
ommended for  invalid  diet.  Sometimes,  in  order  to  make 
a  cocoa  that  shall  be  more  digestible,  a  part  of  the  fat  is  sa- 
ponified by  the  use  of  sodium  hydrate  and  magnesia,  a  pro- 
cess that  may  in  some  cases  produce  a  food  that  is  less 
digestible  than  the  material  that  is  not  so  treated. 

Sweet  chocolate,  especially  by  reason  of  the  sugar  that  is 
added,  has  a  high  food  value.  Chocolate  does  not,  like  tea 
and  coffee,  produce  wakefulness,  though,  on  account  of  the 
large  amount  of  sugar  and  fat  which  it  contains,  it  may  pro- 
duce indigestion.  As  chocolate  is  a  concentrated  food,  it 
may  be  conveniently  used  when  the  weight  of  food  to  be 
carried  must  be  considered,  as  on  the  march,  or  on  camping 
expeditions. 

Experiment  142.  Shake  a  few  grams  of  powdered  chocolate 
in  a  test  tube  with  ether,  filter,  and  allow  the  filtrate  to  evap- 
orate spontaneously  in  a  glass  evaporating  dish.  Notice  the 
taste  and  odor  of  the  fat  or  "  cocoa  butter  "  that  remains. 
Notice  also  that  cocoa  butter  gives  a  clear  solution  with 
ether,  while  wax  or  tallow  gives  a  turbid  solution. 

Experiment  143.  Boil  a  few  grams  of  powdered  chocolate 
with  water,  filter  off  10  cc.,  and  treat  the  cold  solution  with 
iodine  reagent  for  starch. 

COLA 

The  cola  nut  grows  on  a  small  tree  in  several  tropical 
countries  especially  Jamaica,  Africa,  East  India,  and  Ceylon. 
It  contains  caffein,  theobromin,  tannin,  and  the  other  con- 
stituents of  tea  and  coffee.  As  a  beverage  it  is  made  into 
an  infusion  like  coffee,  and  is  served  with  milk  and  sugar. 


BEVERAGES  269 


COMPARISON  OF  THE  COMMON  STIMULATING 
BEVERAGES 

These  beverages  possess  qualities  in  common  for  which 
they  are  universally  esteemed  by  mankind.  First,  they  re- 
tard the  retrograde  metamorphosis  of  the  body  tissues,  and 
thus  enable  the  work  of  the  individual  to  be  done  upon  a 
smaller  supply  of  food  material  and  with  less  fatigue. 

Second.  When  used  in  moderation,  they  are  all  more  or 
less  stimulating  to  the  mental  powers. 

Third.  They  act  as  sedative  to  the  nervous  system.  The 
similarity  of  the  action  of  these  beverages  is  due  to  the  pos- 
session of  common  constituents.  While  there  are  diver- 
gences from  each  other,  in  their  finer  shades  of  action  their 
value  depends  upon  the  aromatic  and  volatile  oil  which  modi- 
fies the  action  of  the  alkaloid.  It  is  an  interesting  fact  that 
similar  properties  are  developed  in  each  of  them  by  roast- 
ing and  drying. 

Coffee  is  more  stimulating  than  cocoa.  It  is  apt  to  cause 
irregularity  and  palpitation  of  the  heart  and  may  disorder 
digestion  if  boiled  too  long. 

Tea  is  the  most  refreshing  and  stimulating  of  these  bev- 
erages. Used  in  excess,  however,  it  powerfully  affects  sta- 
bility of  the  motor  and  vasomotor  nerves,  the  action  of  the 
heart  and  the  digestive  functions,  producing  dyspepsia, 
tremulousness,  irregular  cardiac  action,  headache,  etc. 

Mate  is  supposed  to  be  intermediate  in  its  effects  between 
tea  and  coffee.  Chocolate  is  more  nutritious  than  tea  or 
coffee  on  account  of  the  amount  of  fat  which  it  contains; 
although  much  of  this  fat  is  removed  in  making  cocoa. 
Since  but  little  of  the  solid  is  used  in  making  the  beverage 
cocoa  or  chocolate,  the  food  value  is  not  very  great.  Cocoa 
and  chocolate  are  only  slightly  stimulating  in  their  effects. 

Cola  probably  has  a  restraining  influence  on  tissue  waste 


270  SANITARY  AND   APPLIED  CHEMISTRY 

and  is  mildly  stimulating  to  the  heart  and  nervous  system. 
As  it  will  increase  the  endurance,  it  may  be  used  when 
severe  muscular  exercise  is  to  be  undertaken. 

When  we  consider  the  whole  subject  of  beverages  of  this 
class,  it  is  extremely  interesting  to  notice  that  uncivilized 
people  and  civilized  people  in  different  ages  of  the  world,  in 
different  climates,  and  under  entirely  different  circumstances, 
have  chosen  plants  to  use  in  the  manufacture  of  beverages 
that  contain  these  alkaloid  principles;  caffein  in  the  case 
of  tea,  coffee,  and  cola,  and  theobromin  in  the  case  of  choco- 
late. Most  of  them  also  contain  the  astringent  principle 
tannin.  The  use  of  these  beverages  has  increased  from  year 
to  year  in  all  civilized  countries. 


CHAPTER  XXIII 


ALCOHOLIC  BEVERAGES 

IT  is  probably  true  that  alcohol,  as  such,  is  not  found  in 
sound  fruit,  yet  alcohol  is  so  readily  formed  by  the  process  of 
fermentation  of  sugar,  that  it  was  not  strange  that  it  was 
accidentally  discovered,  and  that  beverages  having  intoxi- 
cating qualities  should  have  been  used  very  early  in  the 
history  of  the  world.  Alcohol,  C2H5OH,  is  a  colorless 
liquid,  having  an  agreeable  odor,  burning  with  a  blue  flame, 
and  having  a  specific  gravity  of  .792.  Ordinary  alcohol  is 
about  95  %  strength,  and  the  remaining  5  %  is  water. 
Proof  spirit,  as  it  is  called,  contains  42.50  %  of  alcohol  by 
weight  or  50  %  by  volume.  This  was  originally  named  from 
being  the  most  dilute  spirit  which  when  lighted  would  fire 
gunpowder. 

The  annual  consumption  of  alcoholic  beverages,  per  cap- 
ita, in  the  United  States,  and  in  several  other  countries,  in 
1900,  was :  — 


GALLONS 

Beer 

Wine 

Spirits 

30.31 

.39 

1.02 

6.10 

21.80 

1.84 

Germany     

25.50 

1.34 

1.84 

Japan,  all  liquors  (mostly  sake')     .    .    . 
United  States  

12.30 

.44 

6.25 
.84 

271 


272  SANITARY    AND   APPLIED   CHEMISTRY 

The  Statistical  Abstract  of  the  United  States  for  1903 
reports  the  per  capita  consumption  of  distilled  spirits  to  be 
1.46  proof  gal. ;  that  of  wine,  0.48  gal. ;  and  that  of  malt 
liquors,  18.04  gal.  There  is  a  notable  increase  in  the  con- 
sumption of  malt  liquors  from  year  to  year. 

Alcoholic  beverages  may  be  made  from  any  vegetable 
product  that  contains  starch  or  sugar.  There  are  four 
general  classes,  viz. :  — 

1.  Fermented  liquors :  as  wine,  cider,  perry ;  wine  from 
fruits,  berries,  etc. ;  palm  wine,  called  "  toddy "  in  India ; 
bouza,  made  in  Tartary  and  the  East  from  millet  seed; 
honey  wine,  used  in  Abyssinia ;  koumiss,  made  from  mare's 
milk  in  Tartary ;  fig  wine,  made  in  the  vicinity  of  the  Medi- 
terranean Sea ;  and  pulque,  made  by  the  Mexicans  from  the 
juice  of  the  century  plant. 

2.  Malt  liquors :  as  lager  beer,  ale,  porter,  stout ;  kvass, 
made  in  Eussia  from  rye ;  chica,  made  in  South  America 
from  corn,  rice,  etc.;  sake,  made  in  Japan  from  rice;  and 
pombe,  made  in  Africa  from  rice. 

3.  Distilled  liquors :  as  alcohol,  whisky,  brandy,  gin,  and 
rum,  and  vodka  made  from  grains  in  Russia,  arrack  made 
from  rice  and  palm  juice  in  India,  mescal  or  pulque  brandy, 
and   cherry  brandy,  or  "  Kirsch-wasser,"  as  it  is  termed, 
in  Germany. 

4.  Liqueurs  and  cordials :  as  absinthe  and  vermuth. 
The  fermented  liquors  are  made  from  the  juices  of  fruits, 

which  contain  sugar,  and  they  require  no  yeast  to  start  the 
fermentation,  but  depend  on  the  germs  which  are  present  in 
the  natural  juices.  Most  of  the  sugar  present  in  fruits  is  in 
the  form  of  invert  sugar.  As  the  quantity  of  alcohol  that  can 
be  obtained  from  any  fruit  juice  is  dependent  on  the  amount 
of  sugar  contained,  a  consideration  of  the  sugar  content  is 
important. 


ALCOHOLIC   BEVERAGES 


273 


The  following  analyses,  by  Fresenius,  show  the  amount 
of  sugar  and  acid  in  the  common  fruits :  — 


PER  CENT 
SUGAR 


PER  CENT  FREK 
MALIC  ACID 


Grapes 16.15 

Sweet  cherries 16.30 

Sour  cherries 10.44 

Mulberries 10.00 

Apples 9.14 

Pears 8.43 

Gooseberries 8.00 

German  prunes 7.56 

Currants 7.30 

Strawberries 6.89 

Blackberries 5.32 

Raspberries 4.84 

Green  grapes 4.18 

Plums 2.80 

Apricots 2.13 

Peaches    .  1.99 


.80 

.88 

1.52 

2.02 

.82 

.09 

1.63 

1.08 

2.43 

1.57 

1.42 

1.80 

.67 

1.72 

1.25 

.85 


•WINE 

The  most  important  of  the  fermented  beverages  is  wine. 
The  cultivation  of  grapes,  for  the  purpose  of  making  wine, 
began  in  the  East  in  the  earliest  times,  and  extended  along 
the  shores  of  the  Mediterranean  Sea.  Germany,  Austria, 
France,  Italy,  Spain,  and  Portugal  are  the  continental  wine- 
growing countries,  while  in  the  United  States  the  industry 
is  of  great  importance  in  Ohio,  New  York,  Virginia,  and 
California.  The  quality  of  the  wine  depends  on  the  variety 
of  grapes,  the  soil,  climate,  and  even  on  the  weather. 

In  order  to  make  genuine  wine,  the  grapes  are  allowed 
to  ripen,  so  that  they  contain  as  much  sugar  as  possible. 
The  grapes  are  carefully  crushed  and  pressed,  and  the  first 
juice  that  runs  off  produces  the  best  quality  of  wine.  The 


274  SANITARY  AND   APPLIED   CHEMISTRY 

"  marc,"  as  the  pulp  is  called,  is  sometimes  pressed  several 
times  after  being  soaked  with  water,  and  this  affords  cheaper 
qualities  of  wine.  The  "  must,"  as  the  pressed  juice  is  called, 
is  allowed  to  ferment  from  10  to  30  days.  Fermentation  be- 
gins at  from  10°  to  15°  C.,  and  is  brought  about  by  the  germs 
which  grow  at  the  expense  of  the  saccharin  and  albuminous 
substances  present,  and  change  the  sugar  to  carbon  dioxid 
and  alcohol.  Thus :  — 

06^06  =  20^0  +  200,. 

Sugar  Alcohol        Carbon  dioxid 

After  the  first  fermentation,  the  wine  is  drawn  off  from 
the  "lees"  and  put  in  casks,  where  the  after  fermentation 
takes  place.  The  "  lees  "  consist  of  the  fungus  growth,  some 
calcium  salts,  coloring  matter  and  "argols,"  potassium 
bitartrate,  or  "  cream  of  tartar,"  which  is  insoluble  in  dilute 
alcohol.  This  is  the  only  practical  source  of  cream  of  tartar ; 
consequently  this  chemical  commands  a  good  price. 

From  60  Ib.  to  70  Ib.  of  "must"  can  be  obtained  from 
100  Ib.  of  grapes.  The  quantity  of  sugar  in  the  juice  va- 
ries from  12  to  30%.  It  is  of  importance  that  the  ferment 
be  of  a  certain  kind  to  produce  a  good  wine ;  and,  indeed, 
the  bacteriologist  has  begun  to  propagate  special  cultures  of 
a  pure  yeast  to  produce  wine  of  a  desired  flavor.  The  wine 
is  stored  in  casks  for  some  months,  for  the  process  of  aging. 
Before  being  placed  in  the  cask,  the  wine  is  treated  with 
isinglass,  or  egg  albumen,  and  "  racked  off  "  from  the  depos- 
ited impurities.  It  must  not  be  too  freely  exposed  to  the 
air,  as  there  is  danger  that  the  alcohol,  by  the  aid  of  the 
acetic  ferment,  shall  be  changed  to  acetic  acid,  according 
to  the  reaction, — 

C2H5OH  +  2  02  =  C2H3O.OH  +  2  H20. 

During  the  aging  process  a  variety  of  fragrant  ethers,  as 
acetic  ether,  malic  ether,  etc.,  are  formed,  which  produce 
an  agreeable  odor  or  bouquet.  Wines  are  sometimes  aged 


ALCOHOLIC   BEVERAGES 


275 


and  at  the  same  time  preserved,  by  pasteurization,  which 
consists  in  heating  them  for  some  time  at  60°  C.,  with  a 
limited  supply  of  air. 

In  regard  to  the  changes  that  take  place  in  the  cask, 
Leach  observes  that  the  alcoholic  strength  of  the  wine  rises. 
This  is  due  to  the  fact  that  the  water  of  the  wine  soaks  into 
the  wood  more  than  the  alcohol  does,  and  is  lost  by  evapo- 
ration, so  that  the  wine  becomes  more  concentrated.  As 
the  water  so  lost  is  replaced  by  the  addition  of  more  wine, 
the  increase  in  the  proportion  of  alcohol  is  rendered  all  the 
greater.  In  the  cask,  too,  a  partial  oxidation  of  the  tannic 
acid  takes  place.  This  causes  the  white  wines  to  become 
darker  in  color,  but  has  just  the  reverse  effect  upon  the  red 
wines ;  for  the  oxidized  tannic  acid  unites  with  and  precipi- 
tates some  of  the  pigment. 

The  alcoholic  strength  of  the  wine  is  somewhat  increased 
by  a  further  fermentation  of  the  sugar.  By  the  oxidation 
of  some  of  the  alcohol  to  acetic  acid,  compound  ethers  are 
formed.  There  is  an  impression  that  wine  continues  to  im- 
prove with  age,  and  "  old  wine  "  is  highly  prized.  Some  of 
the  stronger  wines  improve  for  a  few  years,  but  not  for  an 
indefinite  time,  and  wines  often  begin  to  deteriorate  after  a 
short  time.  The  "  extract,"  as  the  term  is  used  below,  is 
what  remains  upon  evaporation. 

The  following    table  gives  the   composition  of   a   few 

wines  :  — 

COMPOSITION  op  WINES 


ALCOHOL 

EXTRACT 

FKBE  ACID 
TABTAKIO 

SUGAR 

ASH 

French  red 

7.80 

2.97 

.58 

.46 

.26 

French  white 

10.84 

1.26 

.44 

.88 

.20 

Spanish  red 

12.34 

3.84 

.57 

.25 

.75 

Calif,  red 

10.03 

2.11 

.64 

.25 

.34 

Calif,  white 

11.16 

11.80 

.63 

.20 

.17 

276  SANITARY   AND   APPLIED   CHEMISTRY 

SWEET  WINES 


ALCOHOL. 

EXTRACT 

FREK  Aon> 
TABTABIC 

BUOAB 

Asa 

Champagne    . 

9.60 

14.34 

.58 

.75 

.16 

Port  .... 

16.29 

8.30 

.38 

6.26 

.25 

Sherry   .     .    . 

15.93 

5.00 

.48 

2.76 

.56 

Madeira     .     . 

15.49 

5.61 

.41 

3.18 

.33 

CLASSIFICATION    OF    WINES 

Wines  are  either  natural  or  "fortified."  Natural  wine 
contains  no  added  alcohol  or  sugar.  When  the  pure  juice  of 
the  grape  is  allowed  to  ferment,  if  it  contains  sufficient 
sugar,  the  amount  of  alcohol  will  continue  to  increase  till 
the  wine  contains  about  15%,  and  this  amount  of  alcohol 
prevents  any  further  fermentation.  Hock  and  claret  are 
usually  of  this  class.  When  alcohol  is  added  to  the  wine 
it  is  said  to  be  "fortified."  Port  and  Madeira  are  often 
treated  in  this  way. 

Wines  are  divided  into  red  and  white  wines,  from  the 
color ;  also  into  dry  wines,  or  those  in  which  all  the  sugar 
has  been  changed  to  alcohol ;  and  sweet  wines,  or  those  in 
which  some  sugar  still  remains,  although  these  are  often 
reinforced  by  the  addition  of  grape  sugar.  Dry  wines  are 
consequently  slightly  sour.  Wines  are  also  divided  into 
"still"  wines,  or  those  in  which  the  carbon  dioxid  gas 
has  been  allowed  to  escape ;  and  effervescent  wines,  in 
which  the  carbon  dioxid  has  been  retained  in  the  liquid 
under  pressure. 

Grapes  make  better  wine  than  other  fruit  because  the 
potassium  bitartrate  (KHC4H406)  is  precipitated  as  the 
alcohol  becomes  stronger  in  the  process  of  fermentation. 
Other  fruits  and  berries,  on  the  other  hand,  contain  citric, 
malic,  or  succinic  acids,  and  the  salts  of  these  are  not  pre- 


ALCOHOLIC   BEVERAGES  277 

cipitated  during  fermentation,  and  so  this  wine  has  not  the 
agreeable  taste  that  characterizes  grape  wine. 

ADULTERATION   OP    WINES 

The  adulterations  of  wine  are  very  numerous.  Plaster  of 
Paris  is  often  used  abroad  for  the  adulteration  of  wines,  but 
native  wines  and  those  imported  into  the  United  States  are 
usually  free  from  this  material.  This  is  done,  it  is  said,  to 
clarify  it,  to  improve  the  color,  to  make  the  fermentation 
more  complete,  and  to  improve  the  keeping  qualities.  On 
the  other  hand,  this  process  is  supposed  to  leave  some 
injurious  compounds  in  the  wine.  The  reaction  due  to 
"plastering"  is  as  follows  :  — 

2  KHC4H406  +  CaS04  =  CaC4H406  +  H2C4H406  +  K2S04. 

Pot.  bitartrate         Cal.  sulfate        Cal.  tartrate          Tartaric  acid       Pot.  sulfate 

In  France  there  is  a  law  against  the  addition  of  more  than 
a  limited  quantity  of  plaster  of  Paris  to  wines  intended  for 
home  consumption.  Not  over  .2%  of  potassium  sulfate  is 
allowed  to  be  present.  The  wine  manufacturers  also  burn 
sulfur  in  the  casks  so  that  the  sulfur  dioxid  shall  artifi- 
cially age  the  wine.  This  tends  to  decrease  the  number  of 
germs  that  would  be  injurious  in  fermentation.  The  addi- 
tion of  cane  sugar,  called  "  chaptalising  "  in  France,  is  prac- 
ticed, under  certain  very  carefully  guarded  conditions,  to  in- 
crease the  yield  of  alcohol,  and  commercial  glucose  is  used  in 
the  same  way.  In  Germ  any  the  addition  of  sugar  to  "  musts  " 
deficient  in  this  material,  is  permitted.  A  cheap  wine  is 
sometimes  put  upon  the  market  which  contains  no  juice  of 
the  grape  whatever,  but  is  made  from  cider  as  a  basis,  to 
which  is  added  alcohol,  tannin,  glycerin,  glucose,  cream  of 
tartar,  orris  root,  ethereal  oils,  and  frequently  osnanthic 
ether.  An  extract  is  frequently  made  from  raisins,  which 
is  colored  and  flavored  to  imitate  wine. 


278  SANITARY   AND   APPLIED   CHEMISTRY 

Wine  is  subject  to  numerous  diseases,  such  as  souring, 
ropiness,  bitterness,  and  molding.  Poor  wines  or  those 
that  have  deteriorated  are  sometimes  distilled  to  make 
brandy. 

Experiment  144.  Test  a  small  portion  of  wine  in  a  test 
tube  for  grape  sugar,  by  the  Fehling  test. 

Experiment  145.  Evaporate  10  cc.  of  wine  to  one  half 
its  volume  on  a  water  bath,  and  to  the  solution  add  50  cc. 
of  a  mixture  of  alcohol  and  ether.  Put  this  solution  in  a 
flask  and  allow  to  stand  tightly  corked  for  some  time,  and 
notice  the  acid  potassium  tartrate  which  crystallizes  out. 

Experiment  146.  Acidify  a  sample  of  wine  with  hydro- 
chloric acid,  heat  to  boiling,  and  add  a  few  drops  of  barium 
chlorid.  If  there  is  more  than  a  trace  of  barium  sulfate, 
"  plastering  "  of  the  wine  is  indicated.  Normal  wine  does 
not  contain  over  .06  %  of  sulf uric  acid  calculated  as  potas- 
sium sulfate. 

CIDER 

The  fresh  juice  of  the  apple,  known  as  sweet  cider,  is  a 
very  convenient  solution  for  growth  of  the  yeast  Saccha- 
romyces  apiculatus,  which  starts  fermentation,  and  so  cider 
does  not  long  remain  sweet.  The  crushed  apples  are  pressed 
in  a  cider  press,  and  the  juice  is  then  run  off  into  barrels 
and  allowed  to  ferment.  The  refuse  left  after  the  juice  has 
been  expressed  is  called  "  pomace,"  and  is  utilized  in  some 
other  industries.  (See  p.  219.)  In  some  countries  more  care 
is  used  in  the  preparation  of  this  beverage,  and  it  is  clarified 
by  the  use  of  gelatin  and  racked  off  or  filtered  from  the  de- 
posited matter.  This  process  tends  to  improve  the  quality 
of  the  cider. 

Cider  contains  from  3  to  7%  of  alcohol  by  volume,  besides 
malic  acid,  sugar,  extractives,  and  mineral  salts. 


ALCOHOLIC   BEVERAGES  279 

ADULTERATION   AND   FALSIFICATION   OF  CIDER 

There  are  found  on  the  market  samples  of  cider  made  by 
adding  water  to  the  pomace,  and  repressing ;  but  this  cider 
is  more  frequently  used  as  a  basis  for  the  manufacture  of 
other  beverages.  The  most  important  sophistications  of 
cider  are  water,  sugar,  and  especially  the  use  of  preserva- 
tives. The  preservatives  most  commonly  used  are  benzoic 
acid,  salicylic  acid,  sulfurous  acid  or  sodium  sulfite,  and 
betanaphthol.  Mustard  seeds,  borax,  and  horse  radish  are 
also  used.  From  some  experiments  by  the  author :  it  was 
shown  that  the  effect  of  those  substances  is  to  retard  the 
fermentation,  and  not  to  ultimately  prevent  it.  It  is  prob- 
ably true  that  substances  that  will  retard  fermentation  will 
also  have  a  tendency  to  produce  indigestion.2  (See  Chapter 
XXV.)  Substances  which  have  a  proper  place  when  used  as 
medicines  should  not  be  taken  in  small  doses  with  the  food 
from  day  to  day.3 

Perry,  or  pear  cider,  is  made  and  consumed  more  exten- 
sively abroad  than  in  the  United  States.  It  does  not  differ 
essentially  except  in  flavor  from  cider. 

Experiment  147.  To  test  for  salicylic  acid  in  cider  or 
beer,  acidulate  a  sample  with  sulf  uric  acid  and  shake  with 
a  mixture  of  equal  parts  of  ether  and  petroleum  naphtha. 
Eemove  the  ethereal  layer  with  a  pipette  and  allow  to  evapo- 
rate to  small  volume  on  a  watch  glass.  Add  a  little  water 
and  a  few  drops  of  ferric  chlorid  solution,  when  the  pres- 
ence of  salicylic  acid  will  be  indicated  by  a  violet  color. 

1  Kas.  Univ.  Quar.,  VI,  A,  p.  111. 

2  Shepard,  Keport,  Ohio  Food  Commis.,  1904. 
8  Harrington,  "  Practical  Hygiene,"  p.  211. 


280  SANITARY   AND   APPLIED   CHEMISTRY 

BEER 

This  beverage  is  a  representative  of  malt  liquors.  Accord- 
ing to  the  best  authorities,  genuine  beer  should  be  made 
from  malt,  starchy  material,  hops,  yeast,  and  water,  and  noth- 
ing else.  Malt  is  made  by  soaking  barley  in  water  for 
several  days,  then  piling  it  up  on  the  floor  or  "  couching " 
till  it  sprouts  and  the  little  radical  starts  to  grow ;  then 
the  process  of  germination  is  retarded  by  "  flooring,"  as  it  is 
called ;  i.e.  spreading  in  progressively  thinner  and  thinner 
layers  upon  the  floor,  and  germination  is  finally  stopped  by 
drying  the  grain.  The  color  of  the  malt  depends  upon  the 
temperature  at  which  this  drying  is  conducted.  If  dried  be- 
tween 32°  and  37°  C.,  it  forms  a  "pale  malt";  if  from  38° 
to  50°,  a  brown  malt.  In  the  process  of  malting  the  albu- 
minous substances  of  the  grain  are  changed  in  part  to  diastase, 
an  active  ferment,  which  has  the  peculiar  property  of  chang- 
ing starch  to  dextrin  and  then  to  sugar  (maltose).  One  part 
of  diastase  under  favorable  conditions  will  convert  2000  parts 
of  starch  to  sugar. 

The  next  process  is  known  as  "  mashing.  "  This  consists 
in  grinding  the  malt  and  soaking  it  in  water  at  a  tempera- 
ture of  75°  C.  The  change  from  starch  to  sugar  is  still  more 
completely  effected  here.  The  clear  infusion,  called  the 
"  wort,"  is  boiled  with  hops,  and  the  solution  is  cooled  very 
rapidly  to  18°  C.  Yeast  is  added,  in  the  proportion  of  about 
1  gal.  to  100  gal.  of  wort,  and  the  liquid  is  allowed  to  fer- 
ment about  8  days.  It  is  then  drawn  off  into  settling  tanks 
and  finally  into  casks,  and  stored  in  a  cool  place  to  ripen. 
The  yeast  changes  the  sugar  into  alcohol  and  carbon  dioxid, 
in  accordance  with  the  reaction,  — 

CeHjA  =  2  C02  +  2  C2H5OH. 

The  sugar  is  not  completely  eliminated,  as  that  would  inter- 
fere with  the  agreeable  taste. 


ALCOHOLIC   BEVERAGES 


281 


The  following  analyses  of  malt  liquors,  taken  from  various 
sources,  will  give  an  idea  of  their  composition :  — 


SP.  GKAVITI 

WATBE 

ALCOHOL 
BY  WEIGHT 

EXTKAOT 

SUGAR 
(MALTOBE) 

Gnu  AND 
DEXTKIN 

ACID  AS 
LAOTIO 

s 

Milwaukee  lager,  bottled     .    . 

1.0100 
1.0178 



4.28 
4.40 

4.18 
615 

1.10 
2.14 

1.57 
2.54 

.06 
.07 

.20 
.81 

Philadelphia  ale,  bottled  .    .    . 
Pilseu  lager    

1.0059 



6.24 
8.29 

3.46 
422 

.59 
.69 

.90 
2.65 

.28 

.40 

85.85 

4.60 

940 

1.0114 

91.11 

8.86 

5.84 

.95 

8.11 

16 

.20 

Lager  (  beer  )      

1.0162 

90.08 

8.93 

5.79 

.88 

8.73 

15 

.23 

1.0176 

89.01 

4.40 

6.88 

1.20 

3.47 

16 

.25 

1.0213 

87.87 

4.69 

721 

1.81 

3.97 

.17 

.26 

1.0137 

91  63 

2.78 

543 

1.62 

242 

89 

15 

Dublin  stout,  XXX     .... 
Porter    

1.0191 

88.49 

6.78 
4.70 

9.52 
6.59 

5.85 
2.62 

2.09 
3  08 

.25 

.36 

Ale     

1.0141 

89.42 

4.74 

5  65 

1  07 

1.81 

.28- 

.31 

Burton  bitter  ale 

544 

542 

1  62 

2.60 

17 

The  quality  of  the  beer  depends  upon  the  manner  of 
brewing,  the  temperature,  qualities  of  ingredients,  method 
of  storing,  kind  of  water  used,  quality  of  the  yeast,  whether 
"top  yeast"  or  "bottom  yeast,"  and  the  temperature  at 
which  it  is  stored.  The  lager  beer  proper,  or  store  beer, 
should  be  kept  in  a  cool  place  for  several  months  before 
being  used.  Very  much  of  the  beer  in  use  in  the  United 
States  is  what  is  known  as  "  present  use  "  beer.  Bock  beer 
is  a  strong  variety  of  beer  made  for  use  in  the  spring  only, 
and  Weiss  beer  is  a  very  weak  beverage  used  in  Germany. 
Ale,  porter,  and  stout  are  richer  in  alcohol  than  lager  beer. 

In  the  manufacture  of  beer  the  tendency  is  to  use  as  little 
of  expensive  ingredients  as  possible,  so  in  cheap  beers,  part, 
or  all,  of  the  barley  malt  is  replaced  by  some  other  grain,  as 
corn  or  rye,  and  even  a  special  kind  of  glucose  is  added  to 


282  SANITARY   AND   APPLIED   CHEMISTRY 

furnish  a  material  that  will  readily  ferment.  It  is  asserted 
that  sometimes  the  bitter  principle  in  cheap  beer  is  also 
replaced  by  quassia  and  other  bitter  substances.  Most  of 
the  beer  on  the  market  contains  from  2  to  4  %  of  alcohol 
by  weight.  There  are  comparatively  few  adulterations  in 
beer  except  those  mentioned.  Salicylic  acid  is,  however, 
frequently  used  as  a  preservative.  A  kind  of  so-called  beer 
has  been  put  upon  the  market  in  some  prohibition  localities. 
This  often  contains  less  than  2%  of  alcohol,  and  is  sold 
under  a  variety  of  special  names. 

Sakd,  the  favorite  beverage  of  the  Japanese,  is  prepared 
from  rice  fermented  by  the  use  of  a  peculiar  fungus  grown 
for  that  purpose.  It  contains  about  12.5  %  of  alcohol.1 

Experiment  148.  To  show  the  presence  of  alcohol  in  a 
sample  of  wine,  beer,  or  cider,  heat  about  100  cc.  in  a  500  cc. 
flask,  into  the  neck  of  which  is  fitted  the  large  end  of  a  cal- 
cium chlorid  tube.  As  soon  as  the  liquid  begins  to  boil 
slowly,  light  the  vapor  that  escapes  at  the  top,  and  observe 
that  it  burns  with  a  characteristic  alcohol  flame. 

Experiment  149.  Collect  some  of  the  distillate  from  a 
sample  of  malt  or  fermented  liquor,  by  boiling  it  very 
gently  in  a  500  cc.  flask,  to  which  is  fitted,  by  a  perforated 
cork,  a  glass  tube  about  60  cm.  long,  bent  at  an  acute  angle 
above  the  cork.  At  the  other  end  of  the  glass  tube  place 
a  small  flask  or  test  tube  surrounded  by  cold  water.  The 
alcohol  will  condense  in  the  cooled  flask. 

Experiment  150.  Test  some  of  the  alcohol,  first  by  taste, 
second,  by  burning,  third,  by  adding  to  a  sample  about  1  g. 
solid  NaOH  and  a  few  crystals  of  iodine.  The  formation 
of  a  yellowish  crystalline  precipitate  of  iodoform,  CHI3, 
which  has  a  characteristic  odor,  indicates  the  presence  of 
alcohol  in  the  distillate. 

1  Church,  "Food,"  p.  195. 


ALCOHOLIC   BEVERAGES  283 


DISTILLED   LIQUORS 

Distilled  liquors,  such  as  rum,  gin,  brandy,  and  whisky, 
are  made  from  some  saccharine  substance  like  molasses,  or 
some  starchy  substance  like  corn,  rye,  barley,  or  rice.  The 
chemical  action  in  the  case  of  starch  is  first  to  change  the 
starch  by  the  addition  of  ground  malt  to  sugar,  which  is  then 
decomposed  in  the  process  of  fermentation  with  yeast,  into 
alcohol  and  carbon  dioxid.  Diastase,  which  is  present  in  the 
malt,  is  the  active  agent  in  transforming  the  starch  to  sugar. 
This  sugar  is  principally  maltose,  mixed  with  one  of  the 
dextrins.1  After  fermentation  the  alcohol  is  distilled  off, 
and  with  it  some  other  volatile  substance,  especially  ethers, 
which  give  the  characteristic  odor  and  taste  to  the  liquor. 
(See  also  Bread,  p.  160.) 

Originally  the  liquid  actually  distilled  over  was  used 
directly  as  a  beverage.  This  was  about  of  proof  strength, 
and  had  the  characteristic  flavor  of  the  substance  from 
which  it  was  distilled.  Practically,  at  the  present  time,  a 
large  proportion  of  the  liquor  on  the  market  is  made  by 
the  rectifiers,  using  as  a  basis  pure  alcohol  and  "  high 
wines,"  which  are  diluted,  colored,  and  flavored  to  imitate 
the  required  beverage. 

The  method  used  in  making  alcohol  is  to  prepare  what  is 
called  the  mash  by  crushing  the  grain  and  other  starchy 
material  into  a  fine  pulp,  and  soaking  it  with  water,  cooling 
it  quickly,  and  allowing  it  to  ferment  with  yeast.  Some- 
times the  mash  is  made  by  the  use  of  sulfuric  acid,  thus 
converting  the  starch  directly  into  dextrin.  The  mash,  after 
fermentation,  is  distilled  in  an  apparatus  so  arranged  that 
the  alcohol,  as  it  is  volatilized,  shall  be  quickly  cooled  and 
condensed  in  a  coiled  pipe.  Theoretically, — 

1  Jago,  "The  Science  and  Art  of  Bread  Making,"  p.  126. 


284  SANITAKY  AND   APPLIED   CHEMISTRY 

100  parts  of  starch  yield  56.78  parts  of  alcohol, 
100  parts  of  cane  sugar  yield  53.08  parts  of  alcohol, 
100  parts  of  dextrin  yield  51.01  parts  of  alcohol, 
but  practically  this  output  is  not  reached. 

The  last  part  of  the  distillate  usually  contains  more  of  the 
higher  alcohols  of  the  series,  especially  amyl  alcohol,  which 
is  one  of  the  constituents  of  "fusel  oil."  This  is  considered 
one  of  the  most  injurious  ingredients  in  ordinary  liquors. 

Brandy  should  be  made  by  the  distillation  of  wine,  and 
should  obtain  its  odor  and  flavor  from  the  fermented  juice 
of  the  grape.  Practically  in  the  hands  of  the  rectifier,  it 
can  be  made  from  alcohol  diluted,  colored  with  caramel, 
flavored  with  oil  of  cognac,  which  is  distilled  from  the  marc 
or  refuse,  from  the  manufacture  of  wine.  The  flavor  of 
brandy  is  much  improved  by  age,  but  many  processes  of 
artificial  aging  have  been  devised. 

Whisky,  as  originally  made  from  corn,  barley,  or 
potatoes,  had  a  brownish  color,  and  a  peaty  or  smoky  flavor 
that  was  imparted  to  it  by  the  smoke  of  the  peat  fires 
used  in  its  manufacture  in  Scotland  and  Ireland.  This 
flavor  is  now  imparted  to  the  commercial  article  by  the  use 
of  creosote  or  some  similar  compound. 

Rum  was  originally  made  in  the  West  Indies  from 
residue  left  after  the  manufacture  of  cane  sugar  or  from 
molasses,  and  the  peculiar  flavor  it  possessed  was  produced 
by  the  volatile  oils  that  are  developed  in  the  manufacture 
of  sugar  from  cane  juice.  Much  of  it  is  now  manufactured 
by  the  "  rectifier  "  in  a  manner  already  described. 

Gin  was  originally  made  by  the  distillation  of  an  alcoholic 
liquid  with  juniper  berries,  but  at  present  the  rectifier  adds 
to  the  diluted  alcohol,  oil  of  juniper  or  turpentine,  or  both, 
some  aromatic  seeds  and  fruits,  and  redistills  the  mixture. 
Many  roots  and  drugs  are  frequently  added  to  improve  the 
flavor  of  gin. 


ALCOHOLIC   BEVERAGES  285 

Experiment  151.  Alcohol  may  be  made  from  the  fer- 
mentation of  a  saccharine  liquid,  as  follows:  In  a  2-liter 
flask  mix  60  cc.  of  molasses  with  700  cc.  of  water,  and  add  a 
small  amount  of  yeast,  and  set  aside  in  a  warm  place  for 
a  day  or  two.  When  the  mass  foams  and  carbon  dioxid  is 
freely  given  off,  distill  slowly  by  attaching  a  condenser,  or 
a  cork,  through  which  passes  a  long  tube  bent  to  an  acute 
angle,  as  in  Experiment  149.  Examine  the  distillate  by 
taste  and  smell,  and  by  the  test  mentioned  in  Experi- 
ment 150. 

Dr.  Battershall l  says :  "  The  most  prevalent  form  of 
sophistication  with  brandy,  rum,  and  gin  is  the  artificial  imi- 
tations, and  the  direct  addition  of  substances  injurious  to 
health  is  of  unf requent  occurrence.  "  He  believes  that  the 
most  dangerous  ingredient  in  the  fictitious  product  is  the 
fusel  oil,  which  is  a  mixture  of  the  higher  alcohols,  but 
other  authorities  have  made  experiments  with  this  substance, 
and  find  no  injurious  effect,  even  when  considerable  quanti- 
ties mixed  with  whisky  are  taken  for  quite  a  length  of  time. 
It  is  -suggested  that  perhaps  the  compounds  which  make 
some  spirits,  especially  those  which  are  recently  distilled,  or 
"  raw, "  more  injurious  than  those  which  are  "  aged,"  may  be 
other  by-products  of  fermentation,  such  as  furfurol. 

LIQUEURS   OR   CORDIALS 

These  beverages  consist  of  very  strong  alcohol,  flavored 
with  aromatic  substances,  and  often  highly  colored,  with  a 
coal  tar  or  a  vegetable  coloring  matter.  Absinthe,  the  most 
important  of  these,  is  yellowish  green  in  color,  and  contains 
oil  of  wormwood,  a  substance  that  has  a  very  injurious 
effect  on  the  nervous  system,  with  anise,  sweet  flag,  cloves, 
angelica,  and  peppermint.  This  liquor  usually  contains  over 
5Q%  of  alcohol. 

1 "  Food  Adulteration  and  its  Detection,"  p.  192. 


286  SANITARY  AND   APPLIED   CHEMISTBY 

Other  beverages  of  this  class  are  maraschino,  distilled 
originally  from  the  sour  Italian  cherry;  chartreuse  and 
benedictine,  named  from  the  monasteries  where  they  were 
originally  made ;  kummel ;  curaqoa,  made  from  the  rind  of 
bitter  oranges ;  ratafia,  made  in  France  from  fruits ;  angus- 
tura  and  vermuth.  Nearly  all  these  contain  a  large  amount 
of  sugar  and  a  high  per  cent  of  alcohol,  and  are  flavored  with 
various  essential  oils,  herbs,  and  spices. 

PHYSIOLOGICAL   ACTION   OF   ALCOHOL 

The  question  as  to  whether  alcohol  is,  properly  speaking, 
a  food,  or  whether  it  simply  acts  as  a  stimulating  beverage, 
is  one  that  has  occasioned  a  vast  amount  of  discussion. 
The  best  authorities  seem  to  agree  that  there  are  cases 
of  disease  in  which  it  is  the  most  useful  material  that  can 
be  administered.  Professor  Atwater,  who  has  investigated 
the  action  of  alcohol  in  his  respiration  calorimeter,  speak- 
ign  of  its  use  in  disease  says:  "What  is  wanted  is  a 
material  which  will  not  have  to  be  digested  and  can  be 
easily  absorbed,  is  readily  oxidized,  and  will  supply  the  req- 
uisite energy.  I  know  of  no  other  material  which  would 
seem  to  meet  these  requirements  so  naturally  and  so  fully 
as  alcohol.  It  does  not  require  digestion,  is  absorbed  by 
the  stomach  and  presumably  by  the  intestines,  with  great 
ease.  Outside  the  body  it  is  oxidized  very  readily,  within 
the  body  it  appears  to  be  quickly  burned,  and  it  supplies  a 
large  amount  of  energy."  From  one  fifth  to  one  seventh 
of  the  total  calories  of  the  diet  may  be  replaced  by  alcohol. 

The  same  author  says  of  the  results  of  his  experiments, 
that  he  found  that  "  the  alcohol  was  almost  completely 
oxidized.  The  kinetic  energy  resulting  from  that  oxida- 
tion agrees  very  closely  with  the  potential  energy  of  the 
same  amount  of  alcohol  as  measured  by  its  heat  of  combus- 
tion as  determined  by  the  bomb  calorimeter,  and  the  alco- 


ALCOHOLIC   BEVERAGES  287 

hol  served  to  protect  body  protein  and  fat  from  oxidation." 
Alcohol  is  inferior  to  carbohydrates,  however,  to  protect  pro- 
tein of  the  body  from  oxidation.1  As  a  stimulant,  alcohol 
acts  primarily  upon  the  nervous  system  and  the  circulation, 
and  quickens  the  transmission  and  enhances  the  effect  of 
nerve  currents.  Although  alcohol  tends  to  remove  muscu- 
lar fatigue  and  to  increase  the  force  of  muscular  action, 
yet  its  use  is  absolutely  forbidden  to  athletes  in  training, 
and  soldiers  in  the  army  continue  in  better  health  if  they 
entirely  abstain  from  the  use  of  this  substance. 

It  will  be  seen  that  although  alcohol  has  some  right  to  be 
regarded  as  food,  yet  it  is  not  a  food  of  any  practical  im- 
portance, for  it  can  merely  replace  a  certain  amount  of  the 
fat,  and  perhaps  of  the  carbohydrates,  in  the  body,  while  its 
secondary  effects  on  the  nervous  and  vascular  systems  coun- 
teract, to  a  large  extent,  the  benefits  derived  from  the  pro- 
duction of  heat  and  energy  by  its  oxidation.2 

1  Thompson,  "Practical  Dietetics,"  p.  229. 

2  Hutchison,  "  Food  and  Dietetics." 


CHAPTER  XXIV 
FOOD  ACCESSORIES 

A  LARGE  number  of  aromatic  substances,  which  have  no 
direct  food  value  are  prized  for  the  agreeable  flavor  which 
they  impart  to  food.  Condiments  are  by  some  writers  de- 
nned as  the  substances  eaten  with  meat  and  used  with  salt, 
while  the  term  spices  is  restricted  to  those  substances  which 
are  used  with  sugar.  It  is  however  impossible  to  draw  a 
definite  line  between  the  two  classes  of  substances. 

The  spices,  since  they  are  used  only  in  small  quantities 
and  are  quite  expensive,  readily  lend  themselves  to  all  kinds 
of  falsification  and  adulteration. 

The  adulterants  are  usually  of  a  harmless  character, 
and  consist  of  English  walnut  shells,  Brazil  nut  shells, 
almond  shells,  cocoanut  shells,  date  stones,  sawdust,  linseed 
meal,  cocoa  shells,  red  sandal  wood,  Egyptian  corn,  rice  flour, 
ground  crackers,  or  "  hard  tack,"  bran  and  many  other  by- 
products from  milling,  plaster,  corn  meal,  turmeric,  cotton- 
seed meal,  olive  stones,  and  pea  meal.1  Various  mixtures 
of  some  of  the  above  are  prepared  and  colored  to  imitate 
each  of  the  ground  spices  and  put  on  the  market,  at  a  very 
low  price,  for  use  in  spice  mills.  In  most  cases  these  fraudu- 
lent mixtures  can  be  detected  only  by  the  skilled  chemist 
or  microscopist,  so  the  only  safeguard  of  the  housekeeper 
is  to  buy  of  reliable  dealers,  get  the  goods  in  sealed  pack- 
ages, and  to  pay  a  fair  price.  In  most  cases  it  is  safer  to 
buy  the  unground  spice.  A  brief  account  only  of  the  source 
and  properties  of  the  most  important  products  will  be  given. 

1  Rep.  Conn.  Agric.  Exp.  Station,  1898-1904. 
288 


FOOD   ACCESSORIES  289 

Cloves  are  the  dried  flower  buds  of  a  plant  belonging  to 
the  Myrtle  family,  growing  in  Ceylon,  Brazil,  India,  the  East 
Indies,  and  Zanzibar.  The  tree,  which  is  an  evergreen,  is 
usually  less  than  40  ft.  high.  After  the  buds  are  picked 
they  are  laid  in  the  sun  to  dry.  The  volatile  oil  of  cloves, 
which  may  be  distilled  off  with  water,  contains  about  70% 
of  eugenol,  C10H1202.  In  addition  to  the  use  of  the  clove 
"  stock  "  above  mentioned,  "  exhausted  "  cloves,  both  whole 
and  powdered,  —  that  is,  those  which  have  been  deprived  of 
a  portion  of  their  volatile  oil,  —  are  put  upon  the  market 
and  mixed  with  fresh  cloves,  so  that  the  fraud  shall  be  less 
apparent. 

Experiment  152.  Grind  about  15  grams  of  cloves  in  a 
porcelain  mortar  and  introduce  into  a  liter  retort  with 
water  and  boil  for  some  time,  condensing  the  steam  in  a 
flask  floating  in  a  pan  of  water.  Pour  the  distillate  into  a 
tall  tube  and  allow  it  to  stand,  and  the  oil  of  cloves  will  rise 
to  the  surface. 

Cinnamon  is  the  inner  bark  of  a  tree  of  the  Laurel 
family,  which  is  cultivated  in  Ceylon,  Java,  Sumatra,  and 
surrounding  countries.  A  cheaper  and  more  common  cassia 
which  is  also  commercially  known  as  cinnamon,  comes  from 
another  tree  of  the  Laurel  family,  which  grows  in  China 
and  India.  Cassia  buds,  the  dried  flower  of  the  China  cas- 
sia, are  also  upon  the  market.  The  odor  of  cinnamon  is 
due  to  the  presence  of  a  volatile  oil,  which  consists  princi- 
pally of  cinnamic  aldehyde,  C6H5CH :  CH.CHO.  A  "  stock  " 
colored  with  red  sandalwood  is  commonly  used  as  an  adul- 
terant; this  stock  frequently  consists  largely  of  foreign 
barks,  such  as  that  of  the  elm. 

Pepper  is  the  dried  berry  of  the  Piper  nigrum,  a  climbing 
plant  which  grows  in  tropical  countries.  For  preparing 
black  pepper  the  unripe  fruit  is  dried  in  the  sun,  but  to  pre- 
pare the  white  pepper  the  ripe  fruit  is  soaked  in  water  and 


290  SANITARY  AND   APPLIED   CHEMISTRY 

the  skins  are  removed  by  friction.  The  taste  and  odor 
of  pepper  is  due  to  the  presence  of  an  essential  oil,  a  hydro- 
carbon, having  the  formula  C10H18,  and  another  important 
substance  called  piperin,  C17H19N08.  In  addition  to  the  or- 
dinary adulterants  in  ground  pepper,  Egyptian  corn  and 
"  long  pepper  "  are  used,  while  cayenne  pepper  is  often  added 
to  raise  the  pungency  nearer  to  that  of  the  pure  product. 

Ginger  is  the  rhizome  of  the  Zingiber  officinale,  an 
annual  herb  which  is  a  native  of  India  and  China,  and  is 
cultivated  in  the  West  Indies,  Africa,  and  Australia.  Black 
ginger  is  prepared  by  scalding  the  freshly  dug  root,  and 
drying  immediately.  White,  or  "  scraped,"  ginger  is  the 
same  material  that  has  been  scraped  and  sometimes  further 
whitened  by  treatment  with  some  bleaching  agent.  Pre- 
served ginger  is  prepared  by  boiling  the  root  and  curing 
with  sugar.  A  volatile  oil  and  a  pungent  resin  give  to  gin- 
ger its  characteristic  odor  and  taste.  Ginger  is  often  adul- 
terated by  mixing  with  it  ginger  roots  that  have  been  ex- 
hausted with  alcohol.  The  alcoholic  extract  or  water  extract 
is  used  for  the  manufacture  of  ginger  ale. 

Nutmeg  and  mace  occur  in  the  fruit  of  trees  of  the  Myris- 
tica  family,  which  grow  especially  in  the  Malay  Peninsula. 
The  tree  grows  from  20  to  30  ft.  high,  and  produces  flowers 
after  about  the  eighth  year.  The  fruit  is  surrounded  by  a 
fleshy  crimson  covering,  which  when  dried  furnishes  the 
mace  of  commerce,  and  the  hard  seed  the  nutmeg.  This  is 
further  prepared  by  washing  with  milk  of  lime.  Nutmegs 
contain  from  3  to  5%  of  a  volatile  oil.  As  the  whole  nut- 
meg is  used  by  the  cook,  rather  than  a  ground  product, 
there  is  not  much  opportunity  for  adulteration.  Mace  has 
the  usual  adulterants,  and  frequently  a  wild  mace,  known  as 
Bombay  mace,  which  is  practically  without  taste  is  added. 

White  mustard  is  the  seed  of  the  Sinapis  alba,  and  black 
mustard  that  of  the  Sinapis  nigra.  The  plant,  which  is 


FOOD   ACCESSORIES  291 

an  herb,  having  yellow  flowers,  grows  both  in  the  United 
States  and  in  Europe.  Both  varieties  contain  about  35%  of 
a  fixed  oil,  which  can  be  separated  by  heat  and  pressure,  a 
soluble  ferment  called  myrosin,  and  sulfocyanate  of  sina- 
pin,  C16H23N05.  The  black  mustard  contains  potassium  my- 
ronate,  which,  when  moistened  with  water,  forms  the  volatile 
oil  of  black  mustard,  known  to  the  chemist  as  allyl  isothyocy- 
anate,  CSH6CSN".  This  has  a  strong  mustard-like  odor,  and 
the  vapor  excites  tears.  This  oil  produces  blisters  on  the  skin, 
and  hence  the  use  of  the  so-called  "  mustard  plaster."  The 
chief  adulterants  of  ground  mustard  are  wheat,  flour,  or 
starch,  mustard  hulls,  and  turmeric  to  restore  the  yellow 
color  lost  by  the  adulteration  with  a  starch  powder.  Some- 
times cayenne  pepper  is  also  added  to  restore  the  pungency. 

VINEGAR 

Since  most  of  the  vinegar  of  commerce  is  used  in  connection 
with  spices  and  in  the  preparation  of  pickles,  etc.,  its  prop- 
erties may  be  studied  in  this  connection.  Vinegar  is  dilute 
acetic  acid,  C2H402,  flavored  with  the  fruit  ethers,  and  can 
be  made  from  any  dilute  alcoholic  liquor.  The  whole  pro- 
cess of  the  conversion  of  cane  sugar  to  vinegar  would  be  rep- 
resented by  the  equations,  — 

C^H^OU  +  H20  =  2  C6H1206 ; 

Cane  sugar  Invert  sugar 

C«HU06  =  2  C2H5OH  +  2  C02 ; 

Alcohol 

C2H6OH  +  0  =  C2H40  +  H20 ; 

Aldehyde 

C2H40  +  0  =  C2H402. 

Acetic  acid 


292  SANITARY   AND   APPLIED   CHEMISTRY 

The  change  from  alcohol  to  vinegar  is  brought  about  by 
the  ferment  mycoderma  aceti,  found  in  the  "  mother."  The 
conditions  for  this  fermentation  are  an  alcoholic  liquid  con- 
taining not  over  12%  of  alcohol,  an  abundance  of  air,  a  tem- 
perature of  from  20°  to  35°  C.,  and  the  presence  of  the  ferment. 

The  materials  used  are  (1)  wine ;  (2)  other  fermented  fruit 
juices;  (3)  spirits  like  diluted  whisky,  or  residues  from 
the  manufacture  of  sugar;  (4)  malt  wort,  or  beer;  (5) 
sugar  beets.  There  are  several  processes  used  for  the  manu- 
facture of  vinegar  on  a  large  scale,  in  addition  to  the  usual 
process  of  allowing  the  cider  to  ferment  in  an  ordinary 
barrel  in  a  warm  cellar  with  the  bunghole  left  open  for  two 
or  three  years. 

In  France  and  Germany  vinegar  is  made  from  wine  by 
pouring  it  from  time  to  time  into  an  oaken  vessel  which  has 
been  soaked  with  boiling  vinegar,  and  then  siphoning  off  into 
storage  tanks.  The  "  mother  casks  "  are  used  for  a  long  time, 
till  they  contain  a  large  amount  of  argols,  ferment,  etc. 

Another  method  is  by  the  "  quick  vinegar  process, "  which 
was  introduced  by  Schutzenbach  in  1823,  and  is  quite  exten- 
sively used  for  spirit  vinegar  in  Germany  and  the  United 
States,  and  for  malt  vinegar  in  England. 

In  this  process,  an  upright  cask  about  10  ft.  high,  and 
provided  with  a  perforated  false  bottom  about  a  foot  above 
the  true  bottom,  is  filled  with  beech  or  oak  shavings.  Just 
under  the  false  bottom  a  series  of  holes  slanting  downward 
is  bored  entirely  around  the  cask.  The  shavings  are  soaked 
in  warm  vinegar,  and  covered  by  a  wooden  disk  perforated 
with  numerous  holes,  through  which  cords  are  loosely  drawn. 
There  are  also  several  glass  tubes  extending  through  this 
disk  to  assist  in  the  circulation  of  the  air.  After  covering 
the  cask  with  a  wooden  cover  having  a  hole  in  the  center, 
the  dilute  alcoholic  liquor  is  poured  into  the  upper  compart- 
ment and  slowly  trickles  over  the  shavings. 


FOOD  ACCESSORIES  293 

As  the  process  of  oxidation  proceeds,  considerable  heat  is 
developed,  and  this  causes  an  upward  current  of  air  which 
enters  the  cask  below  the  false  bottom,  and  escapes  to  the 
upper  part  through  the  glass  tubes.  By  a  siphon  the  par- 
tially acetified  liquid  is  drawn  off  into  a  second  cask.  With  4  °f0 
of  alcohol  in  the  original  liquid,  good  vinegar  will  be  drawn 
from  the  second  vat.  If  "  vinegar  eels  "  appear,  the  convert- 
ing cask  is  treated  with  vinegar  so  hot  that  when  drawn  out 
it  has  a  temperature  of  50°  C.,  which  kills  the  eels.  When 
spirit  is  used  in  this  process,  a  little  infusion  of  malt  is  added 
to  furnish  organic  matter  sufficient  for  the  growth  of  the 
ferment. 

Wine  vinegar  may  be  red  or  yellowish  in  color,  and  con- 
tains from  6  to  9%  of  absolute  acetic  acid.  Beer  and  malt 
vinegars  are  higher  in  specific  gravity  than  wine  vinegar,  and 
contain  considerable  extractive  matter,  and  from  3  to  6%  of 
acetic  acid.  Cider  vinegar  has  the  odor  of  apples,  and  when 
evaporated  yields  an  extract  that  smells  and  tastes  like  baked 
apples.  It  contains  malic  acid  and  from  3^  to  6%  of  acetic 
acid.  The  acidity  should  never  be  below  3%  and  the  spe- 
cific gravity  should  never  be  less  than  1.015. 

Imitation  vinegars  are  sometimes  made  by  the  use  of  acetic 
acid  distilled  from  wood,  or  from  some  mineral  acid,  and 
flavored  with  acetic  ether  and  colored  with  caramel.  The 
extract  from  this  imitation  vinegar  differs  from  malt 
vinegar  in  not  containing  phosphate,  and  from  wine  vinegar 
in  the  absence  of  tartaric  acid,  and  from  cider  vinegar  in  the 
absence  of  malic  acid. 

The  acidity  of  vinegar  assists  in  the  softening  of  some 
foods,  such  as  beets,  cabbage,  cucumbers,  hard-boiled  eggs, 
corned  beef,  and  lobsters,  but  it  should  not  be  used  in  excess 
on  account  of  its  tendency  to  cause  anemia  and  emaciation. 

Experiment  153.  The  approximate  acidity  of  a  sample  of 
vinegar  may  be  ascertained  by  the  use  of  saturated  lime- 


294  SANITARY   AND  APPLIED   CHEMISTRY 

water.  This  is  made  by  allowing  water  to  stand  for  some  time 
with  frequent  shaking  over  slaked  lime.  The  strength  of  this 
is  very  nearly  th  normal.  To  test  the  vinegar,  2.75  cc.  are 
placed  in  a  small  Erlenmeyer  flask  with  some  water,  and  a 
few  drops  of  phenolphthalein  as  an  indicator,  and  titrated 
with  limewater  contained  in  a  burette.  When  the  pinkish 
color  shows  that  the  free  acid  has  been  neutralized,  read  the 
number  of  cubic  centimeters  of  limewater  used,  and  divide 
this  by  10.  This  gives  the  percentage  of  acid  in  the  vinegar. 

Experiment  154.  To  detect  a  free  mineral  acid  in  vinegar, 
add  to  5  cc.  of  vinegar  5  or  10  cc.  of  water ;  after  mixing 
well,  add  4  or  5  drops  of  an  aqueous  solution  of  methyl-violet 
(one  part  of  methyl-violet  2  B  in  10,000  parts  of  water). 
The  occurrence  of  a  blue  or  green  color  indicates  a  mineral 
acid.1 

Experiment  155.  Caramel  is  often  used  to  color  imitation 
vinegars.  To  detect  this,  place  about  25  cc.  of  the  sample  in 
a  large  test  tube  or  in  a  bottle,  and  add  to  it  about  10  grams 
of  fullers'  earth,  shake  the  sample  vigorously  for  several 
minutes,  and  filter.  The  first  portion  of  the  liquid  which 
passes  through  the  filter  should  be  filtered  again.  Return 
the  filtered  sample  to  original  tube,  and  compare  the  color 
of  this  solution  in  a  similar  tube  with  that  of  an  equal 
quantity  of  vinegar  that  has  not  been  treated.  If  the  treated 
sample  is  considerably  lighter  in  color  than  that  which  has 
not  been  treated,  the  vinegar  is  probably  colored  with  cara- 
mel. Caramel  occurs  naturally  in  malt  vinegar.2 

Experiment  156.  To  obtain  the  acid,  except  sulfuric,  of 
vinegar  free  from  extractive  matter,  pour  250  cc.  of  vinegar 
into  a  flask,  add  to  it  25  cc.  of  dilute  sulfuric  acid,  and 
distill  by  the  use  of  the  simple  apparatus  described  in  Ex- 

1Bul.  66,  U.  S.  Dept.  Agric.,  Bu.  Chem.,  p.  64. 
2  Bui.  100,  U.  S.  Dept.  Agric.,  Bu.  Chem.,  p.  48. 


FOOD   ACCESSORIES  295 

periment  149.     Collect  the  distillate  in  a  flask  and  examine 
its  odor,  taste,  etc. 

SALT 

Common  salt,  Nad,  has  been  used  for  thousands  of  years 
as  an  essential  ingredient  of  foods,  and  as  a  preservative. 
Fortunately,  it  is  found  in  numerous  localities  all  over  the 
world.  In  the  United  States,  the  chief  salt-producing  local- 
ities are  Michigan,  New  York,  Kansas,  and  Ohio,  which  to- 
gether furnish  about  90  %  of  the  total  output,1  and  smaller 
quantities  are  obtained  from  California,  Utah,  West  Virginia, 
Louisiana,  Oklahoma  Territory,  Texas,  and  Pennsylvania. 

Salt  is  obtained  either  as  rock  salt,  which  is  mined  in  sev- 
eral localities,  by  the  evaporation  of  sea  water  or  that  of  salt 
lakes,  or  by  the  evaporation  of  brine,  which  is  obtained  from 
salt  wells  or  borings  into  the  salt  bed.  Most  of  the  table  salt 
of  commerce  is  made  by  the  latter  process.  In  some  localities 
solar  evaporation  is  relied  upon  for  concentration  of  the  brine, 
but  usually  the  brine  is  heated  in  an  open  pan  by  direct  heat 
or  in  a  "Grainer"  by  steam  heat.  Many  producers  are 
introducing  cement  evaporating  pans,  automatic  self-acting 
rakers,  and  vacuum  pans. 

The  brine  when  pumped  from  the  wells  contains  some 
impurities,  and  these,  especially  the  calcium  sulfate,  are 
deposited  when  the  brine  is  first  concentrated,  so  that  in  this 
way  the  brine  can  be  partially  purified  in  the  first  pan, 
before  it  is  run  into  the  evaporating  pans  proper.  The  com- 
position of  a  good  brand  of  salt  is  as  follows :  — 

PIB  CENT 

Sodium  chlorid 97.75 

Insoluble  residue .03 

Calcium  sulfate 1.84 

Magnesium  chlorid .38 

Total  100.00 

1  Bailey,  International  Congress  of  Applied  Chemistry,  Berlin,  1903. 


296  SANITARY   AND   APPLIED   CHEMISTRY 

Most  of  the  salts  on  the  market  contain  from  97  to  99  %  of 
pure  salt.  When  salt  absorbs  moisture  it  becomes  hard  and 
inconvenient  for  domestic  use.  This  is  sometimes  remedied 
by  the  addition  of  a  small  quantity  of  starch  or  some  such 
material. 

Experiment  156  a.  To  test  table  salt  for  starch,  boil  a 
sample  with  water,  allow  to  cool,  and  test  by  tincture  of 
iodine.  The  production  of  a  blue  color  indicates  starch. 


CHAPTER  XXV 
PRESERVATION  OF   FOOD 

IT  is  only  within  the  last  hundred  years  that  any  adequate 
methods  for  the  preservation  of  food  have  been  devised ;  in 
fact,  within  the  last  fifty  years  the  greatest  advances  have 
been  made  in  this  art.  Formerly,  fruits,  vegetables,  and 
meats  must  be  consumed  in  the  locality  where  they  were 
produced,  and  fruits  especially  must  be  used  as  soon  as  ripe. 
In  1804  M.  Appert  of  Paris  found  that  meat  and  other 
organic  substances  would  keep  indefinitely  if  sealed  and  then 
heated  in  boiling  water.  In  1810  he  suggested  the  method 
of  introducing  steam  and  heating,  and  then  sealing,  so  that 
when  the  vessel  cooled  a  vacuum  was  formed. 

Canned  meats  and  fruits  have  been  kept  for  quite  a  number 
of  years,  and  were  found  to  be  in  good  condition.  By  the 
use  of  modern  methods  of  preservation  the  season  for  the  use 
of  each  fruit  has  been  extended ;  and  the  product  of  one 
climate  can  be  transported  to  another  climate  for  consump- 
tion. Meats  and  vegetables  can  be  preserved  for  months,  and 
so  the  variety  of  food  for  man  has  been  greatly  increased. 
Since  the  fermentative  changes  that  take  place  when  food 
is  kept  for  some  time  are  due  to  the  growth  of  various  micro- 
organisms, any  process  which  will  prevent  this  growth  or 
keep  these  organisms  out  of  the  food  will  assist  in  its  pres- 
ervation.- Warmth,  moisture,  and  access  of  germ-laden  air 
are  conditions  favorable  for  the  decomposition  of  food. 

Some  of  the  methods  adopted  for  the  preservation  of  food 
are :  (1)  maintaining  a  low  temperature ;  (2)  drying  so  as  to 

297 


298  SANITARY   AND   APPLIED   CHEMISTRY 

remove  as  much  moisture  as  possible ;  (3)  addition  of  sugar 
or  glucose ;  (4)  the  use  of  saltpeter  or  brine ;  (5)  pickling  with 
vinegar ;  (6)  canning  or  placing  in  a  sterilized  atmosphere ; 
(7)  the  use  of  chemical  preservatives. 

Fermentation  and  decay  take  place  best  at  a  moderately 
high  temperature,  so  cold  storage  is  introduced  not  only  to 
transport  fruits  and  meats  from  one  section  of  the  country 
to  another,  but  also  to  keep  the  food  from  the  season  when  it 
is  abundant  until  the  season  when  it  is  scarce.  Preservation 
by  the  use  of  salt,  smoke,  sugar,  saltpeter,  or  vinegar  fur- 
nish conditions  unfavorable  to  the  growth  of  microorgan- 
isms, and  so  decay  is  prevented.  Dried  or  "jerked"  meat 
will  keep  a  long  time  for  the  same  reason,  especially  in  a 
dry  climate. 

In  smoking  the  meat,  which  is  usually  previously  salted, 
it  is  dried  and  penetrated  by  acetic  acid,  creosote,  and  other 
preservatives  of  the  smoke. 

In  "quick  smoking"  processes  the  meat  is  dipped  several 
times  in  a  solution  of  pyroligneous  acid  (which  is  made 
by  the  distillation  of  wood)  and  dried  in  the  air.  Other 
chemicals  are  frequently  used. 

The  process  of  food  preservation  by  canning  or  protecting 
from  air  and  sterilizing  has  developed  to  an  enormous  extent 
in  the  United  States.  When  we  consider  the  annual  output 
of  100,000,000  cans  of  corn,1  the  same  quantity  of  peas,  and 
150,000,000  cans  of  tomatoes,  besides  millions  of  cans  of 
other  vegetables  and  fruits,  some  idea  of  the  value  of  this 
process  to  the  human  race  is  obtained. 

Fortunately,  too,  most  of  this  food  is  prepared  in  such  a 
way  as  not  to  be  injurious  to  the  system.  The  object  to  be 
attained  in  canning  is  to  destroy  the  microorganisms  of 
various  kinds,  so  it  makes  no  special  difference  whether  a 
little  air  remains  in  the  can  or  not,  as  long  as  the  contents  is 
i  Leach,  "  Food  Inspection  and  Analysis, "  p.  689. 


PRESERVATION   OF  FOOD  299 

perfectly  sterilized,  although  formerly  it  was  held  that  all 
the  air  must  be  excluded. 

In  domestic  practice,  fruit  may  be  preserved  by  packing 
in  glass  cans,  filling  nearly  full  of  water,  adding  some  sugar 
if  desired,  and  then  immersing  the  cans  nearly  to  the  neck 
in  a  vessel  of  cold  water.  The  water  is  heated  to  boiling, 
and  allowed  to  boil  from  15  to  30  m.,  dependent  on  the  size 
of  the  fruit,  and  then  the  cans  are  removed  from  the  water 
and  immediately  sealed.  This  process  has  the  advantage  of 
preserving  the  fruit  whole  and  unbroken. 

Another  method  much  in  vogue  is  to  cook  the  fruit  or 
vegetables,  then  put  it,  while  still  hot,  in  glass  or  tin  cans 
that  have  just  been  taken  out  of  boiling  water,  and  to  seal 
immediately  with  the  ordinary  glass  cover  and  rubber 
washer  or  with  cork  and  sealing  wax. 

The  method  used  at  canning  factories  is,  in  general,  to 
pack  the  material  in  tin  cans,  with  the  required  amount  of 
water,  and  after  sealing  to  cook  with  hot  water  or  steam. 
The  cans  are  then  punctured  to  allow  the  excess  of  air  to 
escape,  again  sealed  with  a  drop  of  solder,  and  again  heated 
for  some  time  to  destroy  all  microorganisms. 

A  more  modern  method  of  canning  is  to  cook  the  fruit  at 
a  temperature  of  82°  to  88°  C.  before  transferring  to  the 
cans,  and  afterward  heat  in  the  cans,  when  sealed,  to  a 
temperature  of  about  125°  C.  in  dry  air  retorts,  so  that  it 
shall  be  completely  sterilized.1  This  process  can  be  fin- 
ished in  a  shorter  time  than  the  former,  and  on  account  of 
the  higher  temperature  employed  is  very  effective. 

Experiment  157.  To  show  the  effect  of  exclusion  of  ordi- 
nary air  from  fruit,  prepare  two  samples  thus  :  Place  some 
hot  apple  sauce  in  two  250  cc.  bottles  that  have  just  been 
heated  with  boiling  water.  In  the  mouth  of  one  bottle 

1  Ibid.  p.  690. 


300  SANITARY   AND   APPLIED   CHEMISTRY 

place  a  perforated  cork,  through  the  opening  of  which 
passes  a  calcium  chlorid  tube  packed  with  cotton,  that  has 
been  heated  in  an  oven  to  120°C.  In  the  mouth  of  the  other 
bottle  place  a  cork  having  a  small  opening  in  it.  Allow 
these  bottles  to  stand  for  a  week  or  more  in  a  warm  place, 
and  notice  the  almost  entire  absence  of  mold  in  the  bottle 
which  is  protected  from  the  microorganisms  of  the  air  by 
the  cotton,  and  the  abundant  mold  on  the  surface  of  the 
sauce  in  the  other  bottle. 

When  canned  food  spoils  if  put  up  in  tin  cans,  the 
can  usually  becomes  convex  on  the  ends,  instead  of  con- 
cave, as  it  is  found  normally,  on  account  of  the  genera- 
tion of  gases  by  fermentation.  It  is  not  an  uncommon 
practice  for  manufacturers  to  puncture  these  "  swells  "  and 
reheat  them  to  stop  fermentation,  and  afterward  solder 
them  again,  and  put  them  on  the  market. 

Since  tin  cans  are  used  in  the  preservation  of  food,  and 
as  the  tin  plate,  as  it  is  called,  from  which  the  cans  are 
made,  often  contains  considerable  lead,  it  is  not  uncommon 
to  find  salts  of  tin,  iron,  and  lead  in  the  canned  products. 
This  is  partly  due  to  carelessness  in  soldering  of  the  cans, 
and  allowing  the  drops  of  the  solder,  which  may  contain 
50%  of  lead,  to  remain  inside  the  can,  and  partly  because 
the  acid  fruits  act  on  the  tin  plate  of  which  the  can  is  com- 
posed. 

Formerly  very  grave  danger  was  apprehended  from  the 
metals  that  might  be  contained  in  canned  goods,  but 
the  fact  is  that  we  have  not  experimentally  proven  whether 
the  small  quantities  that  are  found  have  a  poisonous  effect 
or  not. 

Experiment  158.  To  show  the  presence  of  iron  in  canned 
fruit,  test  some  of  the  juice  from  a  can  of  California  grapes 
(better  one  that  has  been  canned  for  some  time)  with  a 
little  of  a  strong  infusion  of  tea.  Since  the  tea  contains 


PRESERVATION   OP   FOOD  301 

tannic  acid  (Experiment  141)  it  will  form  a  black  coloration 
(ink)  with  the  iron  that  has  been  dissolved  from  the  tin 
plate  by  the  acid  of  the  fruit. 

CHEMICAL   PRESERVATIVES 

In  recent  years  the  practice  of  adding  preservatives  to 
food  has  greatly  increased.  These  preserve  the  foods  by 
preventing  the  growth  of  bacteria.  There  may  be  a  differ- 
ence of  opinion  in  regard  to  the  use  of  some  of  them,  but  it 
seems  perfectly  reasonable  that  antiseptic  substances  which 
will  prevent  the  decay  of  food  will  be  liable  also  to  retard  the 
disgestive  processes.  Food  that  has  really  begun  to  decay 
may,  by  the  use  of  these  preservatives,  be  put  on  the  market 
and  sold  as  wholesome.  It  is  no  defense  of  the  practice  to 
claim  that  food  that  has  been  thus  treated  is  better  than  if 
it  had  not  been  treated,  for  such  food,  which  has  begun  to 
decay  or  ferment,  should  be  condemned  without  question. 

When  preservatives  are  added  to  food  intended  for  the 
use  of  invalids  and  young  children,  they  are  especially 
liable  to  interfere  with  the  digestion  and  prove  injurious 
to  the  system.  Many  tests  have  been  made  upon  the 
lower  animals,  and  some  results  have  been  obtained  which 
indicate  that  some  preservatives  may  be  used  with  impu- 
nity, but  the  time  has  not  come  to  admit  the  use  of  preserv- 
atives in  foods  without  question.  This  position  has  been 
taken  by  the  health  authorities  in  many  states ;  and  where 
the  use  of  these  substances  is  not  actually  prohibited,  they 
require  at  least  that  each  package  so  preserved  shall  be 
labeled  to  that  effect.''! 

In  a  recent  article l  Dr.  Vaughan  says,  "  A  true  food 
preservative  must  keep  the  substance  to  which  it  is  added 
in  a  wholesome  condition  so  that  it  can  be  consumed  by 
persons  in  every  physical  condition  of  life  without  impair- 

1  Jour.  Am.  Med.  Assoc.,  Vol.  XLIV.,  p.  753. 


302  SANITARY   AND   APPLIED   CHEMISTRY 

merit  of  health  or  danger  of  life.  It  is  not  the  function  of  a 
food  preservative  to  impart  to  the  food  a  deceptive  appear- 
ance and  to  make  it  look  better  than  it  actually  is.  The  law 
.  .  .  forbids  the  use  of  all  meat  preservatives  that  restore 
the  color  and  fresh  appearance  to  partially  decomposed 
meats.  ...  To  prevent  the  development  of  those  bacteria 
that  produce  odoriferous  substances  while  the  more  toxic 
bacteria,  that  develop  no  telltale  odor,  continue  to  grow  and 
multiply,  does  not  comply  with  the  requirements  demanded 
by  a  food  preservative  that  asks  for  legal  sanction.  ...  To 
retard  the  multiplication  of  the  lactic  acid  bacillus,  and  thus 
prevent  the  souring  of  milk,  while  colon  bacilli  continue  to 
multiply  uninterruptedly  is  not  the  function  of  a  true  food 
preservative.  .  .  .  The  man  who  adds  formaldehyde  to  his 
milk  takes  down  the  danger  signal,  but  does  not  remove  the 
danger." 

In  regard  to  the  action  of  preservatives  on  the  digestive 
fluids,  it  should  not  be  forgotten  that  preservatives  if 
permitted  in  the  food  are  liable  to  be  taken  by  persons  with 
every  degree  of  digestive  impairment.  The  free  hydrochloric 
acid  of  the  gastric  juice  will  be  neutralized  by  sodium  sulfite, 
if  this  salt  is  used  as  a  preservative,  and  this  cannot  fail  to 
interfere  seriously  with  the  action  of  the  digestive  enzymes. 
It  seems  to  be  well  established  that  formaldehyde  also  inter- 
feres with  their  action.  In  regard  to  some  of  the  other 
preservatives,  sufficient  experiments  have  not  been  made  to 
prove  definitely  that  they  interfere  with  the  digestive  func- 
tions. 

The  author  above  quoted  believes  that  a  food  preservative 
in  order  to  receive  legal  sanction  should  keep  the  food  in  a 
wholesome  condition  and  not  simply  retain  this  appearance 
while  bacterial  changes  continue ;  in  the  largest  quantities 
used  it  should  not  impair  any  of  the  digestive  processes ; 
and  finally  this  substance  must  not  be  a  cell  poison,  or  if  it 


PRESERVATION   OF   FOOD  303 

is  a  cell  poison,  it  must  be  added  to  foods  only  by  persons 
who  have  special  training,  and  not  by  a  manufacturer  who 
has  no  knowledge  of  the  subject.  Foods  containing  these 
preservative  substances  should  also  be  plainly  marked,  so 
that  the  presence  of  the  preservative  can  be  known  to  each 
consumer. 

"If  the  use  of  any  preservatives  is  to  be  permitted  in 
food,  boric  acid  and  sodium  benzoate  are  the  least  objec- 
tionable, since  they  appear  to  have  less  tendency  to  dis- 
turb the  digestive  functions  than  have  the  others." l 

At  the  conclusion  of  an  exhaustive  series  of  experiments 
upon  the  effect  of  boric  acid  and  borax  on  the  general  health, 
Dr.  H.  W.  Wiley  says :  "  It  appears,  therefore,  that  both 
boric  acid  and  borax  when  continuously  given  in  small  doses 
for  a  long  period,  or  when  given  in  large  quantities  for  a 
short  period,  create  disturbance  of  appetite,  of  digestion, 
and  of  health."2 

Some  of  the  preservatives  most  used  are  borax  (Na2B407, 
10  H20),  boric  acid  (H3B03),  salicylic  acid  (HC7H503), 
ammonium  fluorid  (NH4F),  benzoic  acid  (HC7H502),  so- 
dium benzoate  (NaC7H502),  formaldehyde  (HCHO),  sodium 
sulfite  (Na2S03)  and  sulfurous  acid  (H2S03),  beta-naph- 
thol  (Ci0H7OH),  abrastol  Ca(C10H6S03OH)2  and  saccharin 
(C6H4COS02NH).  The  detection  of  small  quantities  of 
these  substances  in  food  usually  requires  the  service  of  an 
experienced  analyst. 

Borax  and  boric  acid  are  often  sold  under  various  names, 
such  as  "  Preservaline,"  and  mixtures  of  borax  with  other 
preservatives  are  also  on  the  market  under  various  trade 
names.  This  preservative  is  used  especially  in  milk  and 
meat  products.  The  method  of  detection  given  under  Milk, 
Experiment  136,  should  be  followed. 

!H.  Leffman,  Jour.  Franklin  Inst.  147  (2),  97-109. 
2  Circ.  15  or  Bui.  84,  U.  S.  Dept.  Agric.,  Bu.  Chem. 


804  SANITARY   AND   APPLIED   CHEMISTRY 

Salicylic  acid  is  a  white  crystalline  powder,  very  soluble 
in  alcohol,  and  soluble  in  500  parts  of  water.  It  is  used 
in  preserving  fruit  products,  beer,  cider,  milk,  etc. 

Experiment  159.  To  test  for  salicylic  acid,  to  50  cc.  of 
the  substance  to  be  tested,  made  feebly  acid  with  a  few 
drops  of  sulf  uric  acid,  add  an  equal  bulk  of  a  mixture  of 
equal  parts  of  ether  and  petroleum  spirit,  and  shake  vigor- 
ously. Allow  the  liquids  to  separate,  and  draw  off  the 
solvent,  or  take  it  out  with  a  pipette,  filter  it,  and  allow  it 
to  evaporate  at  a  gentle  heat.  If  salicylic  acid  is  present, 
fine  silky  crystals  will  usually  be  seen.  Add  to  the  residue 
left  on  evaporation  a  few  drops  of  water  and  a  drop  of 
very  dilute  ferric  chlorid  or  of  ammonium  ferric  alum  solu- 
tion, and  if  there  is  any  salicylic  acid,  a  characteristic  violet 
color  is  produced. 

Sodium  benzoate,  which  is  more  frequently  used  as  a 
preservative  than  benzoic  acid,  is  a  white  granular  powder, 
of  a  slightly  aromatic  odor,  and  disagreeable  taste.  It  is 
readily  soluble  in  water,  and  the  solution  is  used  as  a 
preservative,  especially  for  catsup,  mince  meat,  jams,  and 
jellies. 

Experiment  159  a.  Benzoic  acid  or  a  benzoate  may  be 
detected  in  the  absence  of  salicylic  acid  by  Peter's  method,1 
which  depends  on  oxidation  of  the  benzoic  acid  to  salicylic 
acid  by  treatment  with  sulfuric  acid  and  barium  peroxid, 
and  then  applying  the  ferric  chlorid  test  for  salicylic  acid 
noted  in  Experiment  159. 

Saccharin  acts  both  as  a  preservative  and  a  sweetening 
agent.  It  is  a  white  crystalline  powder,  soluble  in  1000 
parts  of  cold  water.  It  is  four  or  five  hundred  times  as 
sweet  as  cane  sugar. 

Sodium  sulfite  is  a  white  solid  readily  soluble  in  water. 

65,  p.  160,  U.  S.  Dept.  Agric.,  Bu.  Chem. 


PEESERVATION   OF   FOOD  305 

It  has  the  characteristic  taste  of  the  smoke  of  a  burning 
sulfur  match. 

The  sulfites  are  used  especially  to  preserve  meat  and  meat 
products,  and  give  them  a  "natural"  red  color,  and  for 
alcoholic  beverages,  cider,  fruit  juices,  and  catsup. 

Experiment  160.  As  the  test  for  the  detection  of  sulf ur- 
ous  acid  depends  on  converting  it  into  sulfuric  acid,  the 
following  method  may  be  used :  Place  200  g.  of  the  sus- 
pected food,  which,  if  solid,  should  be  ground  with  water 
in  a  mortar,  in  a  flask,  make  acid  with  phosphoric  acid,  con- 
nect with  a  condenser,  and  distill  slowly,  till  20  cc.  have 
come  over.  Boil  this  distillate  in  a  large  test  tube  or  small 
flask  with  bromin  water  and  add  a  few  drops  of  barium 
chlorid.  The  formation  of  a  white  precipitate  of  barium 
sulfate  indicates  that  a  sulfite  was  present. 

Formaldehyde  is  a  gas  that  readily  dissolves  in  water. 
The  40%  solution  is  usually  sold  under  the  name  of  "for- 
malin." The  gas  has  a  characteristic  odor.  It  is  used  as  a 
preservative  for  fish,  broken  eggs,  meat  products,  milk,  etc. 
The  method  of  testing  for  formaldehyde  is  given  under 
Milk,  Experiment  137. 

Experiment  161.  To  some  egg-white,  in  a  porcelain  evapo- 
rating dish,  add  a  moderate  quantity  of  formaldehyde. 
Place  the  dish  over  a  water  bath,  and  warm,  not  above  60°  C. 
for  some  time.  Notice  the  leathery  character  of  the  product. 

Experiment  162.  Saccharin  is  said  by  some  to  have  slightly 
preservative  qualities,  but  it  is  added  to  food  products,  such 
as  canned  sweet  corn,  principally  as  a  sweetening  agent.  For 
its  detection  in  jelly,  preserves,  or  canned  vegetables,  use 
about  20  grams  of  the  sample.  Grind  this  in  a  mortar  with 
about  40  cc.  of  water,  strain  through  muslin,  acidify  with  2  cc. 
of  dilute  sulfuric  acid,  and  shake  moderately  with  ether. 
Separate  the  ethereal  layer  and  allow  this  to  evaporate 


306  SANITARY   AND   APPLIED   CHEMISTRY 

spontaneously  in  a  watch  glass,  and  take  up  the  residue  with 
water.  If  saccharin  is  present,  this  solution  will  have  a  sweet 
taste.  To  confirm  this  test  add  one  or  two  grams  of  sodium 
hydroxid,  place  the  dish  in  an  oil  bath  and  heat  to  250°  C., 
for  twenty  minutes.  This  will  convert  the  saccharin  into 
salicylic  acid.  After  cooling  and  acidifying  with  sulfuric 
acid,  extract  as  usual  and  test  for  salicylic  acid  according  to 
Experiment  159.1 

COLORING  OP  FOOD  PRODUCTS 

This  is  another  method  of  falsifying  food,  and  making  it 
appear  better  than  it  is,  or  of  simulating  wholesome  foods 
with  a  combination  of  entirely  foreign  substances.  The 
coal-tar  colors,  of  which  there  is  an  endless  variety,  lend 
themselves  very  readily  to  the  coloring  of  foods  and  bever- 
ages. The  use  of  these  dyestuffs  is  not  only  liable  to 
lead  to  injury  of  the  health  of  the  consumer  from  the  poi- 
sonous nature  of  the  coloring  material,  but  the  consumer  is 
deceived  so  that  he  buys  the  goods  thinking  they  are  of 
greater  value  than  they  actually  are.  There  are  some  of 
the  coal-tar  or  aniline  colors,  which  are  of  themselves  harm- 
less, but  in  the  process  of  manufacture  some  poisonous  sub- 
stance such  as  arsenic  or  mercury  is  used,  and  a  little  of  this 
remains  in  the  finished  product,  making  it  dangerous  for 
consumption.  It  is  true  that  so  far  as  we  know  the  coal-tar 
colors  are  mostly  harmless,  so  the  chief  cause  for  objection  to 
their  use  is  on  account  of  the  fraud  on  the  consumer.  It  is 
the  custom  with  many  manufacturers  of  confectionery  to  use 
only  such  colors  as  are  accompanied  by  certificates  cf  the 
chemist  as  to  their  purity.  In  some  cases  vegetable  colors, 
such  as  turmeric,  logwood,  annatto,  Brazil  wood,  beets,  and 
safflower  are  used.  The  only  animal  coloring  matter  in 
common  use  is  that  of  the  cochineal,  called  carmine  red. 
1  Bui.  66,  p.  51,  U.  S.  Dept.  Agric.,  Bu.  Chem. 


PRESERVATION   OF   FOOD  307 

Experiment  163.  Test  a  sample  of  tomato  catsup  for  a 
coal-tar  dye  by  the  method  described  in  Experiment  122. 

Salts  of  copper  are  sometimes  used  to  impart  an  artificial 
green  color  to  canned  goods,  particularly  peas,  beans,  brus- 
sels  sprouts,  and  pickles.  An  old-fashioned  method  for 
greening  pickles  was  to  put  a  copper  cent  in  the  vinegar  in 
which  they  were  boiled.  The  practice  of  coloring  food 
material  by  the  use  of  compounds  of  copper  is  more  common 
on  the  Continent  than  in  the  United  States.  Imported  goods 
frequently  contain  considerable  copper.1  Examinations  of 
a  large  number  of  canned  vegetables  greened  by  copper,  as 
bought  in  Massachusetts,  showed  them  to  contain  from  a 
trace  to  2.75  g.  per  can,  calculated  as  copper  sulfate.  The 
author  has  found  in  an  ordinary  pickled  cucumber  the  equiva- 
lent of  one  seventh  of  a  grain  of  copper  sulfate. 

Experiment  164.  Incinerate  fruit  or  vegetables  in  a  por- 
celain evaporating  dish  with  sulfuric  acid,  adding  a  little 
nitric  acid  from  time  to  time  till  the  carbon  is  completely 
consumed.  Add  a  few  drops  of  hydrochloric  acid  to  the 
ash,  filter  into  a  small  test  tube,  and  add  to  this  solution  an 
excess  of  ammonium  hydroxid,  when  a  blue  color  indicates 
the  presence  of  copper. 

1  Leach,  "  Food  Inspection  and  Analysis,"  p.  70. 


CHAPTER   XXVI 
ECONOMY  IN  PREPARATION  OF  FOOD;  DIETARIES 

THE  importance  of  cooking  food  has  already  been  dis- 
cussed (p.  121).  It  is  owing  to  the  practice  of  cooking  food 
that  the  dietary  of  civilized  man  has  been  greatly  en- 
larged and  improved.  Many  kinds  of  food  which  would  be 
not  only  unpalatable,  but  indigestible  in  the  raw  state,  are 
rendered  wholesome  and  nourishing  by  some  process  of  cook- 
ing. So  the  proper  cooking  of  food  may  be  regarded  as  an 
art ;  indeed,  one  distinction  of  a  civilized  man  is  that  he  is 
one  who  prepares  his  food  by  cooking.  Most  foods,  with 
the  exception  of  fruits,  require  cooking ;  animal  foods  espe- 
cially are  cooked  to  make  them  palatable  and  wholesome. 

In  addition  to  what  has  been  said  on  previous  pages 
about  cooking  in  the  case  of  individual  foods,  since  all  the 
different  foods  have  now  been  studied,  some  general  state- 
ments will  be  more  readily  understood. 

In  the  cooking  of  starchy  foods  it  will  be  noticed  that  the 
starch  grains,  as  "  put  up,"  so  to  speak,  by  nature,  are  very 
close  and  compact  in  most  seeds,  so  that  they  will  withstand 
any  natural  temperature,  and  a  moist  as  well  as  a  dry  climate. 
When  these  seeds  are  to  be  used  for  food  they  must  be 
soaked  with  water  and  allowed  to  swell.  By  this  treatment 
the  fine  particles  of  starchy  substances  will  be  in  a  much 
better  condition  to  be  attacked  in  the  process  of  digestion 
by  the  alimentary  liquids.  The  starch  grains  are  rendered 
much  more  digestible  by  being  cooked ;  there  is  less  lia- 
bility that  they  shall  pass  through  the  body  unchanged,  for 

308 


ECONOMY  IN   PREPARATION   OF  FOOD  309 

if  they  are  not  changed  to  sugar  by  the  ptyalin  (see  Ex- 
periment 84)  of  the  saliva,  or  the  juices  in  the  stomach  and 
intestines,  they  do  not  nourish  the  body. 

Fats  undergo  slow  combustion  in  the  body  and  are 
changed  to  carbon  dioxid  and  water,  thus  furnishing  much 
of  the  heat  needed  by  the  body.  If  these  are  too  expensive, 
their  place  may,  to  a  considerable  extent,  be  taken  by  the 
carbohydrates.  In  any  case  the  excess,  or  that  which 
remains  over  what  is  actually  used  up  in  doing  the  work 
required  of  the  body,  is  stored  up,  and  may  be  drawn  upon 
as  a  reserve. 

The  fats  should  be  taken  into  the  system  as  fats  and  not 
as  products  of  the  destruction  of  fats.  In  the  process  of 
digestion  in  the  intestine,  the  fat  is  subjected  to  a  double 
process  of  emulsification  and  saponification,  which  is  brought 
about  by  the  combined  action  of  the  bile  and  the  pancreatic 
juice.  This  process  is  interfered  with,  and  indigestion  is 
produced  when  overheated  fats  are  taken  into  the  system. 
These  volatile  products  which  are  produced  by  the  decompo- 
sition of  the  fats  cause  the  familiar  irritation  of  the  eyes, 
and  a  disagreeable  odor,  when  food  is  fried. 

In  cooking  an  albuminous  food,  as  an  egg,  if  frying  is  the 
method  of  cooking  used,  the  temperature  is  necessarily  so 
high  that  the  egg  albumin  is  rendered  hard  and  partially  in- 
soluble in  the  digestive  fluids.  Oysters,1  when  satisfactorily 
cooked,  are  heated  only  to  boiling,  or  if  fried,  are  sur- 
rounded by  a  batter,  which  protects  the  albuminous  tissues 
from  being  overheated.  A  high  temperature  also  greatly 
decreases  the  digestibility  of  the  gluten  of  grains  and  of 
the  casein  of  milk,  so  the  latter  liquid  is  less  wholesome 
when  boiled. 

Beans  and  peas,  which  contain  both  legumin  and  starch, 

1  Richards  and  Elliot,  "  The  Chemistry  of  Cooking  and  Cleaning," 
p.  61. 


310  SANITARY   AND   APPLIED   CHEMISTRY 

require  considerable  cooking,  to  soften  the  cellulose  and 
make  the  starch  digestible.  If  these  vegetables  are  cooked 
in  hard  water,  there  is  danger  that  an  insoluble  compound 
shall  be  formed,  by  the  combination  of  the  legumin  with 
lime  or  magnesia  in  the  water ;  steaming,  as  previously  sug- 
gested, will  partly  obviate  this  difficulty. 

Again,  in  seeking  for  economy  of  food,  the  question  arises, 
What  food  furnishes  the  largest  amount  of  nutriment  at  the 
most  reasonable  cost  ?  As  we  shall  see  a  little  later,  the 
amount  of  energy  in  terms  of  "calories"  that  each  food 
is  capable  of  producing,  has  been  carefully  determined,  and 
this  will  furnish  a  clew  to  the  value  of  different  foods.  For 
instance,  a  certain  sum  invested  in  bread  will  yield  much 
more  energy  than  the  same  sum  invested  in  milk  or  in  meats. 
Both  the  latter  foods  are  valuable,  but  they  are  not  cheap. 

To  build  up  the  tissues,  a  cheap  form  of  proteid  is  that 
contained  in  peas  or  beans,  while  eggs  are  eight  times  as 
expensive,  and  beef  five  times  as  expensive  at  ordinary 
prices. 

In  general,  vegetable  food  is  cheaper  than  animal  food, 
either  as  a  source  of  energy  or  to  build  up  the  tissues.  The 
reason  for  this  is  evident  when  we  consider  that  the  vegeta- 
ble foods  are  built  up  from  the  simple  substances  found  in  air, 
water,  and  soil,  while  the  food  of  animals  consists  of  highly 
organized  vegetable  or  animal  substances.  One  author  states, 
as  an  illustration  of  the  comparative  cost  of  vegetable  food, 
that  1\  acres  devoted  to  raising  mutton  would  support  a 
man  for  a  year,  while  the  same  amount  devoted  to  the 
growing  of  wheat  would  support  16  men  for  the  same  time. 
It  may  be  said  that  as  the  vegetable  food  is  so  much  more 
bulky  it  would  require  much  more  heat  to  cook  it,  but  with 
the  best  appliances,  the  cost  of  this  additional  fuel  would 
not  counterbalance  the  increased  cost  of  animal  food. 

While  carbohydrates  are  cheap  constituents  of  food,  pro- 


ECONOMY   IN   PKEPARATION  OF   FOOD  311 

teids  and  fats  are  expensive.  If  the  fat  is  derived  from 
animal  sources  this  is  particularly  true,  but  foods  contain- 
ing cotton-seed  oil,  and  the  oil  of  some  varieties  of  nuts, 
furnish  fats  at  a  reasonable  price. 

There  is  no  necessary  relation  between  the  cost  of  a  food 
and  its  nutritive  value,  for  we  pay  for  color,  size,  appear- 
ance, and  flavor,  in  foods,  not  for  their  value  in  feeding  the 
body.  There  is  practically  as  much  nourishment  in  the  cut 
of  beef  costing  8  cents  a  pound  as  in  that  costing  16  cents ; 
a  fine  quality  of  starch  in  the  form  of  arrowroot  or  sago  is 
expensive,  but  the  same  amount  of  starch  of  a  different  fla- 
vor made  from  corn  is  very  cheap ;  a  Roquefort  cheese  costs 
perhaps  50  cents  a  pound,  while  a  cheese  just  as  good  for 
food,  but  made  in  New  York  State,  costs  only  15  cents. 

It  is  important  that  the  right  method  of  cooking  should 
be  selected  for  each  food,  a  method  that  shall  develop  the 
agreeable  flavors  and  make  the  food  as  digestible  as  possible. 
A  cheap  cut  of  beef  may  be  made  appetizing  and  wholesome 
by  careful  and  skillful  cooking,  and  it  is  equally  true  that 
an  expensive  cut  may  be  made  tough  and  tasteless  by  the 
ignorant  cook.  It  is  easy  to  spoil  good  food,  and  render  it 
unwholesome  by  cooking  it  in  fat,  or  by  too  slow  heating. 
Potatoes  maybe  cooked  till  they  are  "mealy"  and  the  sepa- 
rate starch  grains  glisten  in  the  light,  or  they  may  be  water- 
soaked  and  waxy,  and  consequently  slow  to  digest.  It  is 
easy  to  prepare  sour  or  heavy  bread,  overheated  toast,  tough 
beefsteak,  or  muddy  coffee,  but  the  raw  material  costs  just 
as  much  as  if  the  food  product  had  been  made  wholesome 
and  agreeable. 

Great  economy  of  fuel  can  be  secured  by  the  use  of  the 
right  kind  of  stove  or  range,  and  by  utilizing  such  an 
appliance  as  a  "  steamer,"  so  that  half  a  dozen  dishes  can  be 
cooked  at  one  time  over  the  same  fire.  This  latter  vessel  is 
especially  economical  when  gas,  either  natural  or  artificial, 


312  SANITARY   AND   APPLIED   CHEMISTRY 

or  gasoline  is  used  for  fuel  in  cooking.  When  the  water  is 
once  brought  to  a  boiling  temperature  in  the  steamer,  a  very 
small  flame  will  keep  it  boiling,  and  the  contents  of  the 
vessel  will  not  become  appreciably  hotter,  nor  will  it  cook 
much  quicker,  if  it  boils  much  more  tumultuously.  Boiling 
water  means  100  °  C.,  and  it  does  not  get  any  hotter,  except 
under  pressure.  This  is  a  fact  too  often  forgotten  by  the 
cook,  who  is  anxious  to  "hurry  the  dinner." 

Another  interesting  application  of  science  to  the  culinary 
art  is  the  invention  of  the  Aladdin  oven,  by  Edward  Atkin- 
son.1 This  oven  consists  of  a  metallic  chamber  surrounded 
by  nonconducting  material,  and  so  arranged  that  it  can  be 
heated  from  below  with  a  good  kerosene  lamp  or  Rochester 
burner.  Almost  any  food  may  be  cooked  in  this  oven,  and 
it  is  especially  adapted  to  the  preparation  of  soups  and  the 
cooking  of  vegetables.  The  process  depends  on  the  use  of  a 
moderate  heat  for  a  long  time  instead  of  a  high  temperature 
for  a  short  time,  as  in  ordinary  cooking.  As  the  oven  is 
surrounded  by  a  nonconducting  wall,  the  heat  that  is  pro- 
duced cannot  readily  escape.  This  oven  has  been  utilized 
on  a  large  scale  in  preparing  cheap  and  nutritious  food  for 
workmen. 

DIETARIES 

We  have  already  discussed  the  two  general  classes  of 
nutrients  (p.  123)  and  to  some  extent  the  properties  of 
each  class.  Most  of  our  knowledge  of  the  composition 
and  nutritive  value  of  food  has  been  accumulated,  in  the 
United  States  and  Europe,  within  the  past  fifty  years. 
Although  the  analysis  of  milk  was  reported  by  Boussiugault 
and  Le  Bel  in  1831,1  yet  it  was  not  till  Liebig,  Playfair, 

1 "  The  Right  Application  of  Heat  to  the  Conversion  of  Food  Mate- 
rial," Proc.  Am.  Aatoc.  for  Adv.  Science,  1890. 

8  Atwater.  "  Foods,  Nutritive  Value  and  Cost,"  Farmer's  BuL 
23,  U.  8.  Dept.  Agric. 


ECONOMY  IN  PREPARATION  OF  FOOD     313 

Boeckman,  and  others,  about  the  middle  of  the  last  century, 
devised  new  methods  for  the  analysis  of  foods  and  feeding 
stuffs,  that  we  began  to  have  a  definite  knowledge  of  this 
important  subject. 

With  the  adoption  of  the  so-called  Weende  method,  pro- 
posed by  Henneberg  in  1864,  new  impetus  was  given  to  this 
branch  of  investigation,  and  numerous  improvements  have 
been  made,  till  now  chemists  generally  agree  on  the  methods 
of  analysis  to  be  employed.  American  food  products  first 
began  to  be  investigated  in  1878-1881,  by  Professor  Atwater, 
under  the  auspices  of  the  United  States  Fish  Commission, 
and  these  investigations  have  been  carried  on  more  recently 
by  agricultural  colleges,  the  experiment  stations  of  the  va- 
rious states,  and  the  Department  of  Agriculture  of  the  gen- 
eral government.  The  latter  department,  at  an  expense  of 
from  $  10,000  to  $20,000  per  year,  for  the  past  10  years,  has 
extended  these  investigations  on  human  nutrition,  till  at 
the  present  time  we  have  very  complete  data  upon  this 
subject.1 

We  have  already  learned  that  the  analysis  of  a  food  shows 
the  per  cent  of  water,  proteids,  fats,  carbohydrates,  and  min- 
eral salts,  which  it  contains,  and  each  of  these,  with  perhaps 
the  exception  of  water,  has  its  food  value.  In  order  to  com- 
pare the  different  foods,  and  calculate  the  relative  amount 
of  energy  that  can  be  obtained  from  them,  the  ordinary 
method  is  to  determine  the  "heat  units,"  or  "calories,"  that 
can  be  produced  by  the  combustion,  under  standard  condi- 
tions of  a  given  amount  of  food.  Although  the  results  are  not 
exactly  the  same  when  food  is  oxidized  in  the  body  to 
produce  energy,  and  when  it  is  burned  in  a  calorimeter  to 
produce  heat,  yet  this  method  is  convenient  for  classification 
and  computation  of  the  relative  value  of  foods. 

*At-water  and  Woods.  "Chem.  Comp.  of  Am.  Food  Materials," 
Bui.  28,  U.  S.  Dept.  Agric.,  Office  of  Exp.  Stations. 


814  SANITARY   AND   APPLIED   CHEMISTRY 

A  calorie l  is  the  amount  of  heat  that  is  required  to  raise 
the  temperature  of  one  kilogram  of  water  from  0°  to  1°  C., 
or  approximately  the  amount  of  heat  that  would  be  required 
to  raise  one  pound  of  water  4°  F.,  and  is  equal  to  3084  foot- 
pounds. The  "fuel  value"  means  the  total  calories  obtained 
by  the  combustion  of  any  food  substance  within  the  body. 
Considering  the  ordinary  food  materials,  the  following  esti- 
mate has  been  made  for  the  average  amount  of  heat  and 
energy  or  the  "fuel  value"  of  each  of  the  classes  of 
nutrients :  — 

One  pound  of  protein  gives        ....     1860  calories. 

One  pound  of  fats  gives 4220  calories. 

One  pound  of  carbohydrates  gives     .        .        .     1860  calories. 

From  this  it  will  be  seen  that  a  pound  of  protein  of  lean 
meat,  for  instance,  is  about  equal  to  a  pound  of  sugar  or  starch, 
in  yielding  heat  and  mechanical  energy,  and  that  fats  have 
a  fuel  value  about  two  and  a  quarter  times  that  of  the  carbo- 
hydrates or  protein. 

From  the  analyses  of  foods,  to  which  reference  has  been 
made,  it  is  possible  to  calculate  the  fuel  value  of  a  given 
amount  of  any  food  or  of  the  rations  supplied  to  a  number  of 
people. 

Experiments  have  also  been  carried  on  by  W.  0.  Atwater, 
at  the  Wesleyan  University,  in  what  is  known  as  a  "  res- 
piration calorimeter."  In  this  apparatus,  which  is  a  small 
closed  room,  the  experimenter  remains  for  several  days,  and 
all  the  food,  air,  and  water  used  is  weighed  and  passed  in 
to  him,  and  all  the  products  given  off  from  the  body  are 
also  weighed  and  analyzed.  A  careful  record  is  also  taken 
of  the  temperature,  and  if  the  experimenter  works  to  exer- 

1  See  "Foods,  Nutritive  Value  and  Cost, "  Atwater,  also  "Practical 
Dietetics,"  Thompson,  also  ''Air,  Water,  and  Food,"  Richards  and 
Woodman. 


ECONOMY   IN   PREPARATION   OF   FOOD  315 

else  his  muscles,  a  record  is  made  of  the  mechanical  work 
accomplished.  "  The  main  value  of  the  experiments  so  far 
conducted  in  this  calorimeter  consists  in  the  actual  demon- 
stration that  the  law  of  conservation  of  energy  operates 
within  the  body  in  precisely  the  same  manner  as  it  does 
outside."  In  man  it  was  found  that  the  measured  energy 
of  the  food  consumed  by  the  subject  within  the  calorimeter 
was  within  1  %  of  the  calculated  or  theoretical  energy. 

Having  a  knowledge  of  the  composition  of  food,  and  a 
method  for  finding  its  value  as  an  energy  producer,  we  are  in 
a  position  to  study  the  food  of  different  individuals  or  classes 
of  people,  or  to  study  dietaries.  A  dietary,  then,  would  be 
a  known  amount  of  food  of  known  composition,  per  day  per 
person,  and  a  standard  dietary  would  be  such  a  combina- 
tion of  materials  as  furnishes  a  sufficient  amount  of  each  of 
the  nutrient  substances  to  fully  sustain  the  body. 

Professor  Voit  of  Munich  was  one  of  the  first  to  pre- 
pare standard  dietaries,  and  his  work  has  been  supplemented 
by  a  large  amount  of  work  in  the  United  States,  espe- 
cially within  the  last  ten  years. 

It  has  been  recently  pointed  out  that  there  are  two  meth- 
ods of  estimating  dietaries.  One  method  is  by  studying 
the  food  consumption  of  classes  of  people  or  individuals, 
when  they  have  a  free  choice  of  food,  or  when  they  procure 
such  food  as  their  circumstances  allow  them  to  buy.  The 
other  method  contemplates  the  feeding  to  classes  of  individ- 
uals, or  to  selected  persons,  certain  foods  of  known  weight 
and  composition,  and  studying  the  nitrogen  balance,  as  it  is 
called ;  that  is,  the  amount  of  nitrogen  taken  into  the  body, 
daily,  in  the  food,  and  the  amount  excreted.  If  there  is 
more  nitrogen  excreted  from  the  body  than  taken  in,  the 
system  is  evidently  not  fully  nourished.  If  there  is  a  slight 
excess  of  nitrogen  maintained,  the  food  is  sufficient  for  the 
amount  of  work  done  by  the  individual.  An  excess  of 


316 


SANITARY   AND  APPLIED   CHEMISTRY 


nitrogenous  material,  or  of  fat,  may  be  stored  in  the  body 
for  use  in  emergencies. 

Returning  to  the  ordinary  method  of  studying  dietaries, 
some  examples  may  be  given  of  the  results  observed  by 
different  chemists  : l  — 


DIETARIES  * 

PROTEIN 

FATS 

CARBO- 
HYDRATES 

FUBL 

VALU* 

NDTRITIV» 
KATIO 

.Lbs. 

Lbs. 

Lbs. 

Calories 

Ito 

Well-fed   tailors,    Eng- 

land, Playfair      .    . 

.29 

.09 

1.16 

3055 

4.7 

Blacksmiths,  England, 

Playfair  

.39 

.16 

1.47 

4115 

4.7 

Well-fed  mechanics,  Mu- 

nich, Voit    .... 

.34 

.12 

1.06 

3085 

4.0 

Brickmakers,  Munich, 

diet  mainly  corn  meal 

and  cheese,  Hanke     . 

.37 

.26 

1.49 

4540 

5.6 

Brickmakers,  Massachu- 

setts, very  severe  work 

.40 

.81 

2.54 

8850 

11.0 

Professional  men,  Mid- 

dletown,  Ct.,  Atwater 

.27 

.34 

1.08 

3925 

6.6 

University  professors, 

Munich,  light  exercise, 

Kanke     

22 

.22 

.53 

2325 

4.7 

In  the  above  table  the  nutritive  ratio,  mentioned  in  the 
last  column,  is  the  ratio  of  the  protein  to  the  sum  of  all  the 
other  nutritive  ingredients.  The  fuel  value  of  the  fats,  as  pre- 
viously noted,  is  two  and  a  quarter  times  that  of  the  protein 
and  carbohydrates,  so  in  the  calculation  the  quantity  of  fats  is 
multiplied  by  two  and  one  fourth,  and  the  product  is  added 

1  Chittenden,  "Physiological  Economy  in  Nutrition";  also  At- 
water, Inc.  cit. 

8  Per  man  per  day. 


ECONOMY  IN   PREPARATION   OP  FOOD 


317 


to  the  carbohydrates.  This  sum,  divided  by  the  weight  of 
the  protein,  gives  the  nutritive  ratio.  Thus,  in  the  first 
dietary  quoted,  the  ratio  of  protein  to  fats  and  carbohy- 
drates is  as  1  to  4.7. 

Some  standard  dietaries  have  been  compiled  by  Atwater, 
and  represent  what  is  believed  by  the  several  authors  to 
be  the  amount  needed  by  persons  with  different  degrees  of 
labor.  (The  amounts  are  expressed  in  grams.) 


PROTEIN 

FATS 

CARBOHY- 
DRATES 

TOTAL 

FUEL  VALITB, 
OK  CALORIES 

Children,  6  to  15     . 

75 

43 

325 

443 

2041 

Women,  at  moderate 

work,  Voit  .    .    . 

92 

44 

400 

536 

2426 

Man,  at  moderate 

work,  Voit  .   .    . 

118 

56 

500 

674 

3055 

Man,  at  hard  work, 

Voit  

145 

100 

450 

695 

3370 

Hard  labor,  Playfair 

185 

71 

568 

824 

3748 

Man,  at  moderate 

work,  Atwater    . 

125 

125 

450 

700 

3520 

Man,  at  hard  work, 

Atwater      .    .    . 

150 

150 

500 

800 

4060 

Experiment  165.  Study  the  food  used  by  a  family  or  club 
for  a  period  of  several  weeks.  Note  the  actual  weight  of 
all  food  purchased,  the  cost,  and  the  number  of  individual 
meals  taken.  Prom  the  tables  given  by  Atwater,  compute 
the  total  amount  of  protein,  fats,  and  carbohydrates  consumed, 
and  the  amount  per  day  per  capita.  By  the  use  of  the  same 
tables  estimate  the  "  fuel  value  "  of  the  food,  and  the  nutri- 
tive ratio.  Tabulate  the  results  as  in  the  table  quoted  from 
Mrs.  Richards  on  page  319. 

The  daily  amount  of  solid  food  consumed  by  the  adult 
male  is  50  oz.  to  60  oz.,  and  the  water  used  is  about  the 


318  SANITARY  AND   APPLIED   CHEMISTRY 

same.  In  case  of  severe  labor  this  amount  of  food  would  be 
increased  to  75  oz.,  the  addition  being  mostly  in  fats  and  car- 
bohydrates.1 The  standard  ratio  for  health,  of  protein  to  fuel 
ingredients,  has  been  placed  at  1  to  5.8  by  the  Experiment 
Stations  of  the  Department  of  Agriculture. 

According  to  the  standard  dietaries  given  above,  and 
many  others  that  might  be  quoted,  an  average  man  doing 
light  work  would  consume  116  g.  of  protein,  with  suffi- 
cient fat  and  carbohydrates,  to  give  3050  calories;  many 
authorities  would  decrease  this  as  low  as  100  g.  of  protein. 
This  could  be  obtained  from  a  great  variety  of  diet,  either 
largely  vegetable,  or  with  a  moderate  amount  of  animal 
food. 

From  some  recent  experiments  by  Chittenden,2  and  oth- 
ers, upon  several  groups  of  persons,  some  of  whom  lived 
sedentary  lives,  and  others  of  whom  were  athletes  and  sol- 
diers, it  was  shown  that  it  was  possible  to  maintain  the 
nitrogen  balance  and  remain  in  good  health  with  consid- 
erably less  food,  especially  of  the  proteid  class,  than 
the  accepted  dietary  standards  would  indicate.  On  a  diet 
containing  only  42  to  55  g.  of  proteid  matter,  instead  of 
116  to  121,  and  enough  carbohydrates  and  fats  to  make 
1750  calories,  instead  of  3050,  the  men  lived  and  carried  on 
their  daily  work  for  several  months.  This  would  indicate 
that  there  is  a  tendency  to  eat  more  food  than  necessary, 
and  thus  to  overburden  the  excretory  organs. 

The  following  ideal  ration  of  solid  food  is  given  by  Mrs. 
E.  H.  Richards:8  — 

1  Thompson,  "Practical  Dietetics,"  p.  20. 

'"Physiological  Economy  in  Nutrition";  "Economy  in  Food," 
Century  Magazine,  Vol.  70,  p.  859. 

»  "  Chem.  Com.  of  Am.  Food  Material."  Bui.  28,  U.  S.  Dept. 
Agric.,  Office  of  Exp.  Stations.  Also  see  Farmer's  Bui.  23,  U.  S. 
Dept  Agric. 


ECONOMY  IN  PREPARATION  OP  FOOD 


319 


MATERIAL 

AMOUNT 
GRAMS 

PKOTBID 

FAT 

CARBO- 
HYDRATES 

CALORIES 

Bread    .... 

463.6 

31.75 

2.26 

257.28 

1206.82 

Meat     .... 

226.8 

34.02 

11.34 



243.72 

Oysters  .... 

226.8 

12.52 

2.04 



70.01 

Breakfast  Cocoa 

28.3 

6.60 

7.50 

9.60 

135.42 

Milk  

113.4 

3.63 

4.42 

4.88 

75.55 

Broth     .... 

453.6 

18.14 

18.14 

90.72 

316.21 

Sugar     .... 

28.3 





27.36 

112.17 

Butter   .... 

14.17 

.14 

12.27 



118.62 

Total  .    .    . 

106.80 

57.97 

389.84 

2574.60 

Here  the  amount  of  proteid  is  nearly  107  g.  or  about  the 
average  suggested  by  the  best  authorities. 

In  studying  dietaries,  it  is  also  a  practical  question  to 
ascertain  what  the  cost  of  food  per  day  per  man  should  be. 
The  habits  of  people  differ  so  widely,  that  while  in  some 
countries  good  and  sufficient  food  can  be  obtained  at  10  to 
15  cents  per  day  per  capita,  in  other  localities  as  much  as 
35  cents  per  day  is  needed  to  procure  satisfactory  food. 
The  following  summary x  of  cost  of  food  in  different  locali- 
ties, and  under  varying  conditions  of  life,  and  showing  the 
amount  of  food  wasted,  is  of  interest:  — 


COST  OF  FOOD 
PURCHASED 

CALORIES 

CALORIES 
WASTED 

NUTRITIVE 
EATIO 

Cents 

Teacher's  family,  Illinois    . 

27 

3975 

700 

1:6.9 

Professional  men,  Connecticut 

25 

3530 

100 

1:6.8 

Mechanics'  Boarding  Club, 

23 

3720 

330 

1:6.1 

Mechanic's  family,  Indiana 

26 

3840 

555 

1:7.9 

Mechanic's  family,  Tennessee 

16 

4435 

345 

1:8.1 

Students'  Club,  Kansas2     . 

18 

3437 

1:7.6 

1  Bui.  91,  U.  S.  Dept.  of  Agric.,  Bu.  Chem.,  1900. 

2  Trans.  Kan.  Acad.  of  Science,  Vol.  XIX. 


820 


SANITARY   AND   APPLIED   CHEMISTRY 


As  some  of  these  figures  were  obtained  several  years  ago, 
they  would  not  indicate  the  cost  of  living  at  the  present 
time,  as  similar  experiments  have  shown  that  it  has  in- 
creased, within  a  few  years,  from  25  %  to  30  %. 

The  waste  of  food  referred  to  covers  the  necessary  loss 
from  skins,  seeds,  bones,  etc. ;  and  evidently,  from  the  great 
difference  in  different  cases,  it  also  covers  a  large  amount 
of  unnecessary  waste. 

From  statistics  collected  in  this  country,  especially  in 
Massachusetts,  and  in  Europe,  an  idea  can  be  obtained  of 
the  proportion  of  income  that  is  ordinarily  used  for  the 
purchase  of  food  by  families  in  different  circumstances : * — 


INCOME 

PER  CBHT 
EXPENDED 
FOR  FOOD 

GERMANY 
Workingmen       

Dollars 
225  -  300 

62 

450-600 

55 

Well-to-do  

750-1100 

50 

GllKAT    lilUTAIN 

Workingmen        

600 

51 

MASSACHUSETTS 
Workingmen       

350-400 

64 

450-600 

63 

Workingmen        

600-760 

60 

Workingmen        

760-1200 

56 

Workingmen       

Above  1200 

61 

When  the  income  is  small,  considerably  more  than  one 
half  is  expended  for  actual  food.  This  surely  leaves  a  very 
small  amount  for  rent,  clothing  and  the  other  necessaries  of 
life.  •  Since  a  sufficient  quantity  of  wholesome  food  is  of  the 
utmost  importance,  the  poor  man  is  justified  in  expending 

1  Farmer's  Bui.  23,  U.  S.  Dept.  Agric. 


ECONOMY   IN  PREPARATION   OF   FOOD  321 

more  than  half  of  his  income  to  provide  his  family  with  that 
which  they  need  to  give  them  health  and  strength.  It  is 
unfortunately  true,  however,  that  even  the  most  intelligent 
people  know  less  of  the  source,  uses,  and  actual  value  of 
their  food  for  fulfilling  its  important  purpose,  than  they  do 
of  almost  any  of  the  other  daily  necessities. 

It  is  estimated  that  at  least  10  %  of  the  income  is 
squandered  not  only  by  the  well-to-do,  but  frequently  also 
by  those  who  have  a  very  small  income  and  so  can  ill  afford 
it,  in  expensive  food  material  which  affords  little  nutrition, 
in  unsatisfactory  methods  of  preparation,  in  selecting  foods 
out  of  season,  by  throwing  away  much  valuable  food  material, 
and  by  using  badly  constructed  cooking  appliances.  Much 
careful  investigation  is  needed  along  these  economic  lines, 
and  painstaking  instruction  will  ultimately  improve  these 
conditions  which  are  at  present  so  much  deplored. 


BIBLIOGRAPHY 


THE  following  books  and  periodicals  will  be  found  con- 
venient for  reference.  A  more  complete  bibliography  on 
foods  is  found  under  the  individual  topics  in  "  Leach  on 
Food  Inspection  and  Analysis."  An  excellent  bibliog- 
raphy on  the  general  subjects  discussed  in  this  book  may 
be  found  in  Richards  and  Woodman's  "Air,  "Water,  and 
Food." 


AUTHORS 

BOOKS 

PUBLISHERS 

Abady. 

Gas  Analysis  Manual. 

Spon  &  Chamberlain,  New 

York. 

Allen. 

Commercial  Organic  Anal- 

Blakiston's   Sons   &   Co., 

ysis.    Vol.  1,  2,  3,  4. 

Philadelphia. 

Bailey. 

Mineral  Waters  of  Kansas. 

Kans.  State  Univ.,  Geolog. 

Vol.  VII. 

Survey. 

Bailey  and  Cady. 

Laboratory  Guide  to  Study 

Blakiston's    Sons    &   Co., 

of  Qualitative  Analysis. 

Philadelphia. 

Barry.     • 

Hygiene    of    the   School- 

Silver,    Burdett     &    Co., 

room. 

Boston. 

Bartley. 

Medical  Chemistry. 

Blakiston's    Sons    &   Co., 

Philadelphia. 

Barwise. 

Bacterial   Purification    of 

C.  Lockwood  &  Son,  Lon- 

Sewage. 

don. 

Battershall. 

Food  Adulteration  and  its 

E.   &   F.    N.    Spon,    New 

Detection. 

York. 

Benedict. 

Chemical  Lecture  Experi- 

Macmillan Co.,  New  York. 

ments. 

Benedikt  and 

Chemistry    of    Coal    Tar 

Geo.  Bell  &  Sons,  London, 

Kneeht. 

Colors. 

1889. 

Bergey. 

Methods  for  Determination 

Smithsonian    Inst.,  Wash- 

of Organic  Matter  in  Air. 

ington. 

323 


324 


BIBLIOGRAPHY 


AUTHORS 

BOOKS 

PUBLISHERS 

Billings. 

Ventilation  and  Heating. 

Engineering  Record,  New 

York. 

Bissell. 

Household  Hygiene. 

Hodges,  New  York. 

Black. 

Forty  Years  in  the  Medical 

Lippincott   Co.,    Philadel- 

Profession. 

phia. 

Blyth. 

Dictionary  of  Hygiene  and 

Griffin  &  Co.,  London. 

Public  Health. 

Blyth. 

Food,    Composition      and 

Griffin  &  Co.,  London. 

Analysis. 

Bowditch. 

Coal  Gas,  Analysis,  Valua- 

E. &  F.  N.  Spon,  London. 

tion,    Purification    and 

Use  of. 

Catlin. 

Baking  Powders. 

Rnmford  Chemical  Works, 

Providence,  R.  I. 

Chittenden. 

Studies    in    Physiological 

Scribner's  Sons,  New  York. 

Chemistry. 

Chittcnden. 

Physiological  Economy  in 

Stokes  Co.,  New  York. 

Nutrition. 

Church. 

Food. 

Chapman  &  Hall,  London. 

Clarke. 

Elementary  Chemistry. 

American  Book  Co.,  New 

York. 

Crook. 

Mineral  Waters  of  United 

Lea  Brothers  &  Co.,  Phila- 

States and  their  Thera- 

delphia. 

peutic  Uses. 

Dammer. 

Handhnch  der  Chemischen 

Ferdinand  Enke,  Stuttgart. 

Technologic. 

Davis. 

Potable  Waters. 

The  Author,  Des  Monies. 

Davis. 

Chemistry  for  Schools. 

Scott,    Foresman    &    Co., 

Chicago. 

Duckwall. 

Canning  and  Preserving. 

Pittsburg     Printing    Co., 

Pittsburg  Pa. 

Eccles. 

Food    Preservatives    and 

Van  Nostrand  &  Co.,  New 

their  Proper  Uses. 

York. 

Effront. 

Enzymes  and  their  Appli- 

Wiley &  Sons,  New  York. 

cation. 

Eliot. 

Elementary     Manual     of 

American  Book  Co.,  New 

Chemistry. 

York. 

Erdmann. 

Lehr  Buch  der   Anorgan- 

Vieweg    &    Sohn,    Braun- 

ischen Chemie. 

schweig. 

325 


AUTHORS 

BOOKS 

PUBLISHERS 

Fox. 

Sanitary  Examinations  of 

Churchill  Co.,  London. 

Water,  Air,  and  Food. 

Franke. 

Die  Chemie  der  Kiiche. 

Van  Voorst,  London. 

Freer. 

Microorganisms  in  Water. 

Allyn  &  Bacon,  Boston. 

Frankland,   P.  and 

Bacteria  in  Daily  Life. 

Longmans  &  Co.,  London. 

G.   C. 

Frankland,  Mrs. 

Elements  of  Chemistry. 

Longmans  &  Co.,  London. 

Percy. 

Gill. 

Gas  and  Fuel  Analysis  for 

Wiley  &  Son,  New  York. 

Engineers. 

Green. 

Food     Products     of     the 

Hotel  World,  Chicago. 

World. 

Groves  and  Thorp. 

Chemical  Technology. 

Blakiston's    Sons   &  Co., 

Vol.  I.    Fuels. 

Philadelphia. 

Groves  and  Thorp. 

Chemical  Technology. 

Blakiston's    Sons    &   Co., 

Vol.  II.    Lighting. 

Philadelphia. 

Groves  and  Thorp. 

Chemical  Technology. 

Blakiston's    Sons   &   Co., 

Vol.  III.    Gas  Lighting. 

Philadelphia. 

Hardin. 

Liquefaction  of  Gases. 

Macmillan  Co.,  New  York. 

Harrington. 

Practical  Hygiene. 

Lea  Brothers  &  Co.,  Phila. 

Hartshorne. 

Our  Homes. 

Blakiston's    Sons   &   Co., 

Philadelphia. 

Harrop. 

Flavoring   Extracts    with 

Harrop  &  Co.,  Columbus, 

Essences,     Sirups,     and 

Ohio. 

Coloring. 

HassaH. 

Food    Adulterations,   and 

Longmans,  Green  &  Co., 

Methods   for  Detection. 

London. 

Hassler. 

Essentials  of  Chemistry. 

Sanborn  &  Co.,  Boston. 

Hazen. 

Filtration  of  Public  Water 

Wiley  &  Sons,  New  York. 

Supply. 

Holland. 

Medical     Chemistry    and 

W.   B.    Saunders    &   Co., 

Toxicology. 

Philadelphia. 

Hutchison. 

Food  and  Dietetics. 

Wm.  Wood   &  Co.,   New 

York. 

Jago. 

Science  and  Art  of  Bread- 

Simpkin,  Marshall,  Hamil- 

making, Chemistry,  and 

ton,  Kent  &  Co.,  London. 

Analysis  of  Wheat  Flour. 

Jones. 

Principles     of     Inorganic 

Macmillan  Co.,  New  York. 

Chemistry. 

326 


BIBLIOGRAPHY 


AUTHORS 

BOOKS 

PUBLISHERS 

Jones. 

Elements     of      Inorganic 

MacmillanCo.,  New  York. 

Chemistry. 

Kent. 

Steam  Boiler  Economy. 

Wiley  &  Sons,  New  York- 

Kenwood. 

Public  Health  Laboratory 

H.  K.  Lewis,  London. 

Work. 

Konig. 

Chemie  der  Menschlichen 

Julius  Springer,  Berlin. 

Nahrungs   und   Geniiss- 

mittel. 

Lankester. 

^ectures  on  Food. 

Hard  wicks  Co.,  London. 

Lassar-Cohn. 

Chemistry  in  Daily  Life. 

Lippincott    Co.,    Philadel- 

phia. 

Leach. 

Tood  Inspection  and  Analy- 

Wiley &  Sons,  New  York. 

sis. 

Leeds. 

Treatise  on  Ventilation. 

Wiley  &  Sons,  New  York. 

Leff  mann  and  Beam. 

Select    Methods    of   Food 

Blakiston's   Sons   &   Co., 

Analysis. 

Philadelphia. 

Leffmann. 

Sxamination  of  Water  for 

Blakiston's    Sons    &   Co., 

Sanitary  and  Technologi- 

Philadelphia. 

cal  Purposes. 

Lekowitsch. 

Chemical  Technology  and 

Macmillan  Co.,  New  York. 

Analysis  of   Oils,  Fats, 

and  Waxes,  2  vols. 

Letherby. 

On  Food. 

Bailliers,  Tindall  &   Co., 

London. 

Lewes. 

Air  and  Water. 

Methueu  &  Co.,  London. 

-Mallet. 

Water  Analysis. 

National  Bd.  of  Health. 

Mason. 

Water  Supply. 

Wiley  &  Sons,  New  York. 

Newth. 

Chemical  Lecture  Experi- 

Longmans  Green   &   Co., 

ments. 

London. 

Nichols. 

Water  Supply. 

Wiley     &     Sons,       New 

York. 

Paasche. 

Zucker  indnstrie  und  Zuck- 

Gustav  Fischer,  Jena. 

erhandel  der  Welt. 

Pasteur. 

Studies  on  Fermentation. 

Macmillan  Co.,  London. 

Paul. 

Payen's  Industrial  Chem- 

Longmans,  Green  &  Co., 

istry. 

London. 

Pavy. 

Food  and  Dietetics. 

Wood  &  Co.,  New  York. 

Peters. 

Modern  Chemistry. 

Maynard,    Merrill  &  Co., 

New  York. 

BIBLIOGRAPHY 


327 


AUTHORS 

BOOKS 

PUBLISHERS 

Pharmacopoeia      of 

8th  Decennial  Revision. 

Blakiston's    Sons    &   Co., 

United  States. 

Philadelphia. 

Price. 

Handbook  on  Sanitation. 

Wiley  &  Sons,  New  York. 

Rafter. 

Microscopical      Examina- 

Van  Nostrand   Co.,  New 

tion  of  Potable  Water. 

York. 

Rafter. 

Treatment  of  Septic  Sew- 

Van  Nostrand  Co.,    New 

age. 

York. 

Rafter  and  Baker. 

Sewage  Disposal  in  United 

Van    Nostrand  Co.,   New 

States. 

York. 

Ramsay. 

Gases  of  the  Atmosphere. 

Macmillan  Co.,  London. 

Redwood. 

Petroleum   and   its   Prod- 

Griffin &  Co.,  London. 

ucts,  Vol.  I  and  II. 

Remsen. 

Introduction  to  Study  of 

Holt  &  Co.,  New  York. 

Chemistry,  7th  Ed. 

Richards. 

Pood  and  Diet. 

Whitcomb  &  Barrows,  Bos- 

ton. 

Richards. 

Cost  of  Living. 

Wiley  &  Sons,  New  York. 

Richards  and  Elliott. 

The  Chemistry  of  Cooking 

Whitcomb  &  Barrows,  Bos- 

and Cleaning. 

ton. 

Richards  and  Wood- 

Air, Water,  and  Food. 

Wiley  &  Sons,  New  York. 

man. 

Rideal. 

Water  and  its  Purification. 

Lippincott    Co.,    Philadel- 

phia. 

Rolfe. 

The  Polariscope. 

Macmillan  Co.,  New  York. 

Sadtler. 

Industrial  Organic  Chemis- 

Lippincott Co.,    Philadel- 

try. 

phia. 

Schulz. 

Die    Mineral-Trinkquellen 

J.  Abel.  Greifswald. 

Deutschlands. 

Sedgwick. 

Principles  of  Sanitary  Sci- 

Macmillan Co.,  New  York. 

ence  and  Public  Health. 

Simon. 

Manual  of  Chemistry. 

Lea  Brothers  &  Co.,  Phila- 

delphia. 

Smith. 

Foods. 

Appleton  &  Co.,  New  York. 

Snyder. 

Chemistry   of    Plant   and 

Macmillan  Co.,  New  York. 

Animal  Life. 

Spencer. 

Handbook  for  Sugar  Manu- 

Wiley &  Sons,  New  York. 

facturers  and  Chemists. 

Stevenson  and  Mur- 

Treatise on  Hygiene  and 

Blakiston's    Sons    &   Co., 

phy. 

Public  Health. 

Philadelphia. 

BIBLIOQKAPHT 


AUTHORS 

BOOKS 

PUBLISHERS 

Soli. 

Treatise  on  Beverages. 

Sulz  &  Co.,  New  York. 

Packing  House  Industries, 

International    Text   Book 

Cottonseed  Oil,  Manufac- 

Co., Scranton,  Pa. 

ture  of  Leather  and  Soap. 

-—Thompson,  W.  G. 

Practical  Dietetics. 

Apple  ton  &  Co.,  New  York. 

Thorp. 

Outlines      of      Industrial 

Macmillan  Co.,  New  York. 

Chemistry. 

Thresh. 

The  Examination  of  Waters 

Blakist  on's    Sons    &   Co., 

and  Water  Supplies. 

Philadelphia. 

Thudicum. 

Cookery,  its  Art  and  Prac- 

F. Warne  &  Co.,  London. 

tice. 

Thurber. 

Coffee  from  Plantation  to 

American  Grocer  Pub.  As- 

Cup. 

sociation,  New  York. 

Tollens. 

Handbuch  der  Kohlenhy- 

E.  Trewendt,  Breslau. 

drates. 

Tucker. 

Manual  of  Sugar  Analysis. 

Van  Nostrand,  New  York. 

Vaughan  and  Novy. 

Cellular  Toxins. 

Lea  Bros.  &  Co.,  Phila. 

Venable. 

History  of  Chemistry. 

Heath  Co.,  Boston. 

Wanklyn. 

Water  Analysis. 

Triibner  &  Co.,  London. 

Wanklyn. 

Bread  Analysis. 

Triibner  &  Co.,  London. 

Wanklyn. 

Milk  Analysis. 

Triibner  &  Co.,  London. 

Watts. 

Dictionary  of  Chemistry, 

Longmans,  Green   &  Co., 

4Vols. 

London. 

Weichmann. 

Sugar  Analysis. 

Wiley  &  Sons,  New  York. 

Whipple. 

Microscopy    of    Drinking 

Water. 

Wiley  &  Sons,  New  York. 

Wiley. 

Agric.     Chem.     Analysis, 

Chem.  Pub.  Co.,  Easton. 

3  Vols. 

Williams. 

Chemistry  of  Cookery. 

Appleton  &  Co.  ,  New  York  . 

Willoughby. 

Hygiene  for  Students. 

Macmillan  Co.,  London. 

Winton  and  Moeller. 

The  Microscopy  of  Vegeta- 

Wiley &  Sons,  New  York. 

ble  Foods. 

Wood. 

United    States    Dispensa- 

Lippincott  Co.,   Philadel- 

tory. 

phia. 

Yeo. 

Food  in  Health  and  Disease. 

W.  T   Keener  &  Co.,  Chi- 

cago. 

Zipp«rer. 

Manufacture  of  Chocolate. 

Spon  &  Chamberlain,  New 

York. 

BIBLIOGRAPHY 


329 


PERIODICALS 


AUTHORS 

SUBJECTS 

PUBLICATIONS 

Abel. 

Sugar  as  Food. 

U.S.  Dept.  Agri.  Fanner's 

Bui.  13. 

Abel. 

Beans  and  Peas  and  Other 

U.S.    Dept.    Agri.    Office 

Leguminous  Food. 

Exp.  Sta.  Bui.  M. 

Amer.  Chem.  Jour., 

Vols.  1-34. 

Atkinson. 

Cooking  of  Food. 

U.S.  Dept.  Agri. 

Atwater. 

Experiments  in  the  Con- 

U.S. Dept.  Agri.  Exp.  Sta. 

servation  of  Energy. 

Bui.  63. 

Atwater. 

Bread   and  Principles   of 

U.S.  Dept.  Agri.  Farmer's 

Bread  Making. 

Bui.  112. 

Atwater. 

Foods,     Nutritive    Value 

U.S.  Dept.  Agri.  Farmer's 

and  Cost. 

Bui.  23. 

Atwater,  Benedict. 

Exp.    in    Metabolism    of 

U.S.   Dept.    Agri.    Office 

Matter   and  Energy   in 

Exp.  Sta.  Bui.  69. 

the  Human  Body. 

Atwater,  Woods, 

Metabolism    of    Nitrogen 

U.S.  Dept.  Agri.  Exp.  Sta. 

Benedict. 

and     Carbon     in     the 

Bui.  63. 

Human  Organism. 

Atwood. 

A  Study  of  Cider  Making. 

U.S.  Dept.   Agri.    Bu.  of 

Chem.  Bui.  71. 

Atwood. 

Chemical  Composition  of 

U.S.  Dept.  Agri.    Bu.   of 

Apples  and  Cider. 

Chem.  Bui.  88. 

Bailey. 

Recent  Progress  in  the  Salt 

Internationales  Kong,  fuer 

Industry  in  the  U.S. 

angewandte  Chem.  1901. 

Bigelow. 

Composition  of  American 

U.S.     Dept.     Agri.     Div. 

Wines. 

Chem.  Bui.  59. 

Bigelow  and 

Some  Forms  of  Food  Adult. 

U.S.  Dept.  Agric.  Bu.  Chem. 

Howard. 

Bui.  100. 

Bigelow. 

Food  and  Food  Control. 

U.S.  Dept.  Agri.  Bu.  Chem. 

Bui.  69.  Pt.  2  &  4.    Bui. 

83,  Pt.  2. 

Bigelow. 

Analysis  of  Foods. 

U.S.   Dept.  Agri.   Bu.  of 

Chem.  Bui.  65. 

Bigelow,  Gore. 

Studies  in  Apples. 

U.S.   Dept.  Agri.    Bu.  of 

Chem.  Bui.  94. 

330 


BIBLIOGRAPHY 


AUTHORS 

SUBJECTS 

PUBLICATIONS 

Bigelow,  Gore, 

Studies  on  Peaches. 

U.S.    Dept.   Agri.  Bu.  of 

Howard. 

Chem.  Bui.  97. 

Causse. 

Recherches  sur  la  contami- 

Storck, Lyons. 

nation  des  Eaux. 

Chase,  Tolman, 

Chemical   Composition  of 

U.S.    Dept.  Agri.   Bu.  of 

Munson. 

some  Tropical  Fruits  and 

Chem.  BuL  87. 

their  Products. 

Corbett. 

Tomatoes. 

U.S.  Dept.  Agric.  Farmer's 

Bui.  200. 

Duggan. 

Cultivation  of  Mushrooms. 

U.S.  Dept.  Agric.  Farmer's 

Bui.  204. 

Gibson. 

Dietary  Studies. 

Univ.   of   Mo.    Exp.    Sta. 

Bui.  31. 

Grindley 

Losses   in  cooking  Meat, 

U.S.  Dept.  Agric.  O.  Ex.  Sta. 

etc. 

Buls.  102,  141,  162. 

Jour.  Amer.  Chem. 

Soc.  Vols.  1-27. 

Jour.    Chem.     Soc. 

Vols.  38-64. 

Jour,  of  Soc.  of  Chem. 

Industry,  Vols.  1-24. 

Jordan. 

Dietary  Studies  in  Maine 

U.S.    Dept.    Agri.    Office 

State  College. 

Exp.  Sta.  Bui.  37. 

Kebler. 

Adulterated     Drugs     and 

U.S.  Dept.  Agri.    Bn.    of 

Chemicals. 

Chem.  Bui.  80. 

Langworthy. 

Eggs   and    their    uses    as 

U.S.  Dept.  Agri.  Farmer's 

Food. 

Bui.  128. 

Leffman. 

Milk  Inspections  and  Milk 

Medical    News,    Feb.    2, 

Standards. 

1895. 

Logan. 

The  Underground  Waters. 

Miss.  Agri.  Exp.  Sta.  Bui. 

89. 

Mallet. 

Creatin  and  Creatinin. 

Exp.  Sta.  Bui.  66. 

McFarlane. 

Flavoring  Extracts. 

Int.    Rev.    Dept.  Canada, 

Bnl.  89,  etc. 

Miller. 

Baking  Powders. 

Fla.  As.  Ex.  Sta.  Bui.  52. 

Muuroe. 

Chemicals  and  Allied  Prod- 

12th Census  U.S.  No.  210, 

ucts. 

Jun.  25,  1902. 

Mnnson,  Col  man, 

Fruits  and  Fruit  Products. 

U.S.   Dept.   Agri.    Bu.  of 

Howard. 

Chem.  Bui.  66. 

BIBLIOGRAPHY 


331 


AUTHORS 

SUBJECTS 

PUBLICATIONS 

Norton. 
Palmer. 

Food  Adult,  in  Ark. 
Chemical  Survey  of  Wa- 
ters of  Illinois. 

Ark.  Ag.  Ex.  Sta.  Bui.  88. 
Univ.  of  111. 

Parola. 

Canned  Fruit,  etc. 

U.S.  Dept.  Agric.  Farmer's 
Bui.  203. 

Proceedings  Int. 
Congress  Appl. 

Chem. 

Berlin,  1903. 

Richardson. 

Foods  and  Food  Adulter- 
ants. 

U.S.   Dept.   Agri.   Bu.    of 
Chem.  Bui.  13,  Prt.  2. 

Robinson. 

Breakfast  Foods. 

Mich.  Exp.    Sta.   Div.   of 
Chem.  Bui.  21. 

Short. 

Fat  in  Milk. 

Univ.  of  Wis.  Agri.  Exp. 
Sta.  Bui.  16. 

Siosson, 

Composition  of    Prepared 
Cereal  Foods. 

Wyom.  Exp.  Sta.  Bui.  33. 

Smith. 

Sewage  Disposal   on    the 
Farm  and  Protection  of 

Farmer's  Bui.  43. 

Snyder. 

Snyder. 
Snyder. 

Drinking  Water. 
Studies     in     Bread     and 
Bread  Making. 
Milling  Tests  of  Wheat 
Digestibility  and  Nutritive 
Value  of  Bread. 

Minn.Ag.  Exp.Sta.Bul.101. 

Minn.  Ag.  Ex.  Sta.  Bui.  90. 
Minn.  Ag.  Ex.  Sta.  Bui.  126. 

Snyder,  Frisky, 
Bryant. 

Snyder,  Voorhees. 
Squibb. 
Stone. 
Taylor. 

Composition   and  Digesti- 
bility  of   Potatoes  and 
Eggs. 
Bread  and  Bread  Making. 
Alcohol. 
Dietary  Studies. 
Food  Products. 

Minn.  Ag.  Ex.  Sta.  Bui.  43. 

Minn.  Ag.  Ex.  Sta.  Bui.  67. 
U.S.  Pharm.  1890. 
Purdue  Univ.  Bui.  32. 
U.S.     Dept.     Agri.     Diy. 
Microsc.,  Vol.  1. 

Teller. 

Chemistry  of  Wheat 

Ark.  Ag.  Ex.  Sta.  Buls.  42, 
53. 

Tolman,  Munson. 
Wait. 

Olive  Oil  and  its  Substi- 
stute. 
Effects  of  Muscular  Work 
upon     Digestibility     of 
Food    and    Metabolism 

U.S.    Dept.  Agri.    Bu.  of 
Chem.  Bui.  77. 
Exp.  Sta.  Bui.  89  &  117. 

of  Nitrogen. 

332 


BIBLIOGRAPHY 


AUTHORS 

SUBJECTS 

PUBLICATIONS 

W«dderburn. 

Food  Adulteration. 

U.S.  Dept.  Agri.  Dir.  of 

Chem.  Bui.  25. 

Wedderburn. 

Food  and  Drug  Adultera- 

U.S. Dept.  Agri.  Div.   of 

tion  Laws. 

Chem.  Bui.  41. 

We  Ida. 

Analysis  of  Chocolate  and 

Univ.  of  Kans. 

Cocoa. 

Wiley. 

American    Wines   at    the 

U.S.  Dept.  Agri.   Bu.  of 

Paris  Exposition,  1900. 

Chem.  Bui.  72. 

Wiley. 

Foods  and  Food  Adulter- 

U.S. Dept.  Agri.  Div.  of 

ants. 

Chem.,  Bui.  13.    Prts.  4, 

5,  6,  7,  8,  9. 

Wiley. 

Sweet  Cassava. 

U.S.    Dept.  Agri.    Bu.  of 

Chem.  Bui.  44. 

Wiley. 

Mannfac.  of  Starch  from 

U.S.     Dept.     Agric.    Div. 

Potatoes  and  from  Cas- 

Chem. Bui.  58. 

sava. 

Wiley. 

Zinc  in  Evaporated  Apples. 

U.S.  Dept.  Agri.  Div.  of 

Chem.  Bui.  48. 

Williams. 

Food  Analysis. 

U.S.   Dept.  Agri.  Bu.  of 

Chem.  Cir.  20. 

Woods,  Merrill. 

Investigations  on  Digesti- 

U.S. Dept.  Ag.  Office  Exp. 

bility     and      Nutritive 

Sta.  Bui.  86. 

Value  of  Bread. 

Woods. 

Meats,    Composition    and 

U.S.  Dept.  Agri.  Farmer's 

Cooking. 

Bui.  36. 

STATE  REPORTS 

Conn.  Agri.  Exp.  Sta.  Reports  for  1887, 1897, 1898, 1899;  1900,  part*  244; 

1901, 1902,  parts  3  &  4 ;  1903,  parts  2,  4,  6 ;  1904,  parts  2  &  5. 
Illinois  State  Board  of  Health,  Sanitary  Investigations;  1901. 
Kansas  State  Board  of  Agriculture ;  1887  to  1904. 
Kansas  Academy  of  Science,  Vols.  1-20. 

Man.  State  Board  of  Health,  1883,  1890,  1891, 1892,  1893,  1904. 
Minn.  Dairy  and  Food  Commission,  1905. 
National  Board  of  Health  Report,  1882,  &c. 
N.Y.  State  Bd.  Health  Reports. 
New  Hampshire  State  Board  of  Agriculture,  Vol.  13, 
Wisconsin  Dairy  and  Food  Commission,  Nos.  6,  6,  7. 


INDEX 


Acid,  acetic  in  vinegar,  304. 

benzoic  in  foods,  304. 

citric,  217,  247. 

lactic,  246. 

malic  in  fruits,  216,  223. 

salicylic  in  foods,  304. 

tartaric,  217. 

tartaric,  manufacture  of,  217. 
Acidity  of  fruits,  216. 
Adulteration  of  milk,  250. 
Adulteration  of  wine,  277. 
Aerated  bread,  156. 
Air,  ammonia  in,  14. 

amount,  necessary  for  respiration, 
41. 

composition  of,  4. 

contamination    of,   by    combus- 
tion, 40. 

determination  of  carbon  dioxid 
in,  11. 

dew-point,  7. 

dust  in  air,  16,  17. 

ground,  20. 

humidity  of,  7. 

hydrogen  sulfid  in,  14. 

in  the  lungs,  6. 

in  public  buildings,  41,  42. 

infectious     diseases     propagated 
in,  19. 

mechanical  mixture,  5. 

methods  of  analysis,  6. 

moist,  weight  of,  8. 

nitric  acid  in,  14. 

of  crowded  rooms,  39. 

ozone  in,  15. 

substances  in  suspension,  16. 

vitiated,  how,  5. 

weight  of  liter,  7,  8. 
Aladdin  oven,  312. 


Albuminoid  ammonia  in  water,  70. 
Albuminous  foods,  309. 

cooking  of,  309. 
Albuminous  substances,  230. 

function  of,  230. 
Albumins,  229. 
Alcohol,  as  food,  287. 

from  bread,  170,  171. 

manufacture  of,  283,  284. 

physiological  action  of,  286,  287. 

properties  of,  271. 
Alcoholic  beverages,  271. 

per  capita  consumption,  271. 

sources  of,  272. 
Algse,  210. 
Almonds,  227. 

bitter,  227. 
Alum,  action  of,  on  system,  163. 

in  bread,  177,  178. 
Alum  baking  powders,  163. 

composition  of,  162. 
Amides,  230. 
Ammonia,  in  the  air,  14. 

free  in  water,  70. 
Ammonium  carbonate,  155. 

use  of,  in  baking,  155. 
Amygdalen,  227. 
Analysis  of  coals,  29. 
Analysis  'of  gases  (table),  5,  6. 
Aniline,  blue,  105. 
Animal  food,  per  capita,  use  of,  232. 
Anthracite  coal,  28. 
Apples,  213. 

flavor  of,  213,  214. 

ripening  of,  213. 
Argol,  217,  274. 
Argon,  discovery  of,  2,  3. 
Arrowroot,  141. 
Arsenic  in  wall  paper,  19. 
Artesian  well  water,  63. 
Asparagus,  209. 


333 


334 


INDEX 


Atmosphere,  1. 
Galileo's  experiments,  1. 
history  of,  1. 

Lavoisier's  experiments,  2. 
Priestley   and    Scheele's   experi- 
ments, 2. 

Rayleigh's    and    Ramsay's    ex- 
periments, 2. 
Atwater,  experiments  by,  314. 

B 

Babcock  tester,  the,  244. 
Baking  bread,  171. 
Baking  crackers,  171. 
Baking  powders,  158-164. 

age  of,  158. 

manufacture  of,  164. 

use  of,  in  baking,  158. 
Bananas,  144. 

composition  of,  145. 

cultivation  of,  144. 

digestibility  of,  146. 

food  value  of,  145. 

industry,  145. 
Banana  flour,  146. 
Barley,  137. 

composition  of,  137. 
Beans,  142,  143. 
Beef,  lean,  232. 

raw,  232. 

roasted,  232. 
Beef  extracts,  234,  235. 
Beef  juices,  234. 
Beer,  280. 

preservatives  in,  2S2. 

varieties  of,  281. 
Beet  sugar,  191. 

diffusion  process,  191. 

history  of  manufacture,  191. 

manufacture  of,  191,  192. 

production  of,  192. 
Beets,  208. 
Beverages,  257. 

alcoholic,  257. 

non-alcoholic,  257. 
Bibliography,  323. 
Bituminous  coal,  28. 
Bluing,  92. 


Bluing,  aniline,  105. 

indigo,  103. 

Prussian  blue,  104. 
Boiling  water  for  disinfection,  113 
Boneblack  niters,  195,  201. 
Borax,  use  in  cleaning,  93. 
Brandy,  284. 

use  of,  in  baking,  155. 
Bread,  154. 

adulteration,  177. 

aerated,  156. 

alum  in,  177,  178. 

analysis  of,  173. 

baking  of,  169,  170. 

brown,  176. 

copper  sulfate  in,  177. 

fermentation  of,  170. 

food  value  of,  174,  175. 

fresh,  172. 

loss  in  baking,  170. 

making  without  yeast,  155. 

not  raised  by  fermentation,  154. 

raised  by  fermentation,  165. 

raising  of,  169. 

stale,  172,  176. 

white,  175. 

why  bad,  176,  177. 
Breakfast  foods,  181. 

analysis  of,  182. 

value  of,  183. 
Burners  and  lamps,  58. 
Burners  for  gas,  31. 
Burning  fluid,  50. 
Butter,  composition  of,  253. 

"Process,  "254. 

"Renovated,"  254. 

structure  of,  253. 
Butter  color,  test  for,  256. 
Butter  fat,  composition  of,  243. 
Butterine,  224,  254. 


Cabbage,  208. 

Caft.  au  lait,  244. 

Caffein,  264. 

Calcium  hypochlorite,  113. 

Calories,  310,  313,  314. 

Calorimeter,  313,  314. 

Camphene,  50. 


INDEX 


335 


Candle  Same,  47. 
Candles,  48. 

dipped  and  molded,  49. 
Cane  sugar,  187. 

properties  of,  197. 
Cane  sugar  group,  124. 
Canned  fruits,  297. 

iron  in,  300. 

metals  in,  300. 

methods  adapted,  297. 

testing  of,  300. 
Caramel  in  vinegar,  294. 
Carbohydrate,  124. 
Carbolic  acid  for  disinfection,  111. 
Carbon,  burning  of,  24. 
Carbon  dioxid,  9. 

amount  in  air,  9. 

cause  of  bad  effects,  10. 

determination  of,  in  air,  11. 

effect  of,  on  system,  10. 

effect  on  a  candle  flame,  11. 

in  closed  rooms,  10. 

properties  of,  9. 

source  of,  9. 
Carbon  monoxid,  13. 

presence  in  air,  14. 
Carrots,  217. 
Casein  in  milk,  245,  246. 
Cassava,  141. 
Catsup,  210. 
Cauliflower,  208. 
Celery,  209. 
Cellulose,  126. 

action  of  chemicals  on,  126. 

basis  of  fuels,  24. 

digestibility  of,  126. 
Cellulose  group,  124. 
Centrifugal,  190,  195. 

use  of,  190. 
Charcoal,  26. 

deodorizer,  109. 

methods  of  making,  26,  27. 
Cheese,  250. 

coloring  of,  251. 

decay  of,  252. 

falsification  of,  253. 

food  value  of,  252. 

tyrotoxicori  in,  252. 
Cheeses,  251. 


Cheeses,  analyses  of,  252. 

different  varieties,  251. 
Chestnuts,  42,  226. 
Chevreul's  researches,  101. 
Chittenden,  experiments  by,  318. 
Chlorid  of  lime  for  disinfection,  113. 
Chlorin  in  water,  71. 
Chocolate,  265,  267,  268. 

action  on  system,  267. 

analyses,  266. 

food  value,  268. 

manufacture  of,  267. 

sweet,  268. 

Cholera  epidemic  in  Messina,  75. 
Chondrin,  230. 
Cider,  278. 

adulteration  of,  279. 

manufacture  of,  278. 

preservation  of,  279. 
Cinnamon,  289. 
City  water  supplies,  73. 
Cleaning,  92. 
Cleaning  agents,  92. 

action  of,  92. 
Cleaning  powders,  92. 
Cloves,  289. 
Coal,  28. 

analyses  of,  29. 

anthracite,  28. 

bituminous,  28. 

cannel,  28. 

lignite,  28. 

semianthracite,  28. 

semibituminous,  28. 
Cocoa,  265. 

amount  imported,  267. 

analyses  of,  266. 

cultivation  of,  265. 

fat,  267. 

nibbs,  267. 

preparation  of,  266. 

shells,  267. 

soluble,  267. 
Cocoa  butter,  267. 
Cocoanut,  oil  of,  224. 
Cocoanuts,  227. 
Coffee,  262. 

action  on  system,  269. 

adulteration  of,  264. 


336 


INDEX 


Coffee,  amount  imported,  267. 

analyses  of,  263. 

caffein,  264. 

cultivation  of,  262. 

history  of,  223. 

preparation,  263. 

preparation  of  beverage,  268. 

roasting,  263. 

source  of,  266. 

substitutes,  265. 
Coke,  29. 
Cola,  268. 

action  on  the  system,  268. 
Collagen,  230. 

Coloring  food  products,  306. 
Combustion,  complete  and  incom- 
plete, 24. 

Compound  flour,  178. 
Condensed  milk,  248. 

composition  of  normal,  248. 

food  value  of,  249. 

manufacture  of,  248. 
Condiments,  288. 
Consumption,  prevalence  of,  40. 
Cooking  of  eggs,  240. 

of  food,  121. 

right  methods  of,  311. 
Copper  in  foods,  207. 

sulfate  for  disinfectant,  112. 

sulfate  in  bread,  177. 

tests  for,  307. 
Corn,  134. 

canned,  298. 

composition  of,  134. 
Corn  meal,  135. 

comparative  value  of,  135. 
Corn  sirup,  200. 
Cornstarch,  14G. 
Corrosive  sublimate,  115. 

solution  of,  115. 
Cost  of  food,  311. 
Cottolene,  224,  226. 
Cottonseed  oil,  224. 
Cottosuet,  226. 
Cracker  baking,  171. 
Crackers,  174. 
Cream,  dried,  249. 

raising  of,  244. 

ripening  of,  253. 


Cream  of  tartar,  273,  274. 

use  in  baking,  257. 
Cream  of  tartar  baking  powders, 
158,  159. 

composition  of,  159. 
Creatin,  231. 

Cremation  to  destroy  refuse,  90. 
Creosote  for  disinfection,  111. 
Crowd  poisoning,  40. 
Crumb  and  crust,  174. 

analyses  of,  174. 


Defecation  of  sugar,  195. 
Delicacy  of  sense  of  taste,  118. 
Dextrin,  148,  280. 

action  of  acids  on,  199. 

made  from  starch,  199. 

properties  of,  149. 
Dextrose,  199,  246. 
Diet,  mixed,  value  of,  119,  120. 
Dietaries,  312,  315. 

estimation  of,  315. 

history  of  investigation,  312,  313. 

in  common  use,  316. 

standard  (Atwater),  317. 
Diffusion  process,  199. 
Dilution,  purification  of  water  sup- 
plies by,  79. 
Disinfection,  boiling  water  for,  113. 

calcium  hypochlorite  for,  113. 

chlorid  of  lime  for,  113. 

copper  sulfate  for,  112. 

corrosive  sublimate  for,  115. 

creosote  for,  111. 

formaldehyde  for,  114. 

hydrogen  peroxid  for,  112. 

iron  sulfate  for,  112. 

mercuric  chlorid  for,  115. 

potassium  permanganate  for,  112. 

sulfur  dioxid  for,  100. 

tests  for,  107. 

zinc  chlorid  for,  112. 
Distillates  from  petroleum,  57. 
Distilled    liquors,    adulteration   of, 

285. 

Drinking  water  and  disease,  74. 
Dry  air  a  purifier,  109. 


INDEX 


337 


Dry  earth,  a  purifier,  109. 

heat  for  disinfection,  110. 

wood,  26. 

Dust    in    air,    infectious    diseases 
propagated,  19. 

methods  of  examination,  17,  18. 

number  of  colonies,  18. 
Dutch  oven,  171. 

E 

Economy  in  preparation  of  food, 
308. 

of  fuel,  311. 
Egg  substitutes,  240. 
Egg  yolk,  composition  of,  239. 
Egg  white,  composition  of,  238. 
Eggs,  238. 

compared  with  meat,  239. 

cooking  of,  240. 

desiccated,  239. 

food  value  of,  239. 

preservation  of,  239. 

use  of,  in  baking,  155. 
Elastin,  230. 
Electric  lights,  60. 
Electricity  used  for  heating,  38. 
Elements  contained  in  the  body, 

222. 

Emulsin,  227. 
Enzymes,  229. 
Ergot,  179. 

Evaporated  milk,  248. 
Experience  in   selection   of   foods, 

119. 

Extract  of  beef,  234,  235. 
Extracts,  flavoring,  221. 


Fat,     amount     of,    from     animal 
sources,  234. 

amount  in  vegetables,  223. 

composition,  297. 

food  value  of,  224. 
Fats,  cooking  of,  233,  309. 

digestion  of,  309. 

edible,  223. 

properties  of,  223. 


Fats  and  oils,  49. 

composition  of,  49. 
Fatty  acid,  separation  of,  49. 
Fermentation,   causes    that   affect, 
169. 

lactic,  246. 
Fibrin,  230. 
Filters,  household,  82. 

Pasteur-Chamberland,  83. 

Worms  and  Fisher,  82. 
Filtration,  80. 

iron  process,  82. 

mechanical,  80. 

sand,  efficiency  of,  81. 

sand  gallery,  81. 
Fire,   use    of,    to    destroy    germs, 

112. 

Fireplace,  use  of,  33,  34, 
Fish,  235,  236. 

analyses  of,  236. 

cooking  of,  236. 

preservation  of,  236. 
Flash  point  of  oils,  52. 

apparatus  used,  52.  . 

Flavoring  extracts,  Mil*   2,<»  t 
Flour,  133. 

adulteration  of,  177. 

compound,  178. 

ergot  in,  179. 
Food,  accessories,  288. 

borax  in,  303. 

breakfast,  181. 

chemistry  of,  117. 

cooking  of,  121. 

cost  of,  311. 

cost  per  day,  319. 

definition  of,  177. 

indigestible  material  in,  122. 

preservation  of,  288,  297,  298. 

skill  in  preparing,  119. 

suited  to  habit,  age,  etc.,  120. 

use  of,  117. 

varieties  of,  120. 

wasted,  319,  320. 
Food  products,  cooking  of,  306. 
Foods,  albuminous,  309. 

animal,  228,  310. 

classification  of,  123,  124,  229. 

cooking  of,  309. 


338 


INDEX 


Foods,  leguminous,  cooking  of,  310. 

nitrogenous,  228. 

predigested,  380,  382. 

synthetic,  121. 

vegetable,  310. 

Formaldehyde    as    a    disinfectant, 
114. 

method  of  using,  114. 
Fruit  sirups,  221. 
Fruits,  212. 

acidity  of,  216. 

analysis  of,  214. 

canning  of,  299. 

cooking  of,  218,  219. 

distribution  of,  212. 

malic  acid  in,  273. 

ripening  of,  212,  214,  215. 

starch  in,  214. 

structure  of,  212. 

sugar  in,  215. 

sugar  in  (table),  273. 
Fuel,  economy  of,  311. 

value  of,  314. 

wood  as,  25. 
Fuels,  23. 

calorie,  definition  of,  23. 

calorific   power  of  combustibles, 

23. 

Fungi,  210. 
Furnaces,  hot  air,  35. 

precautions  in  use  of,  36. 
Fusel  oil,  284. 

G 

Galacto-araban,  215,  216. 
Galactose,  199,  246. 
Garbage,  disposal  of,  90. 
Garlic,  210. 
Gas,  30. 

acetylene,  55. 

advantages  of,  31. 

air,  54. 

artificial,  30. 

bi-producers  of  manufacture,  54. 

burners,  31. 

carbon,  54. 

coal,  53. 

composition  of,  56. 


Gas,  drilling  wells,  30. 

fuels,  31. 

illuminating,  53. 

lights,  incandescent,  59. 

methods  of  making,  53. 

natural  and  artificial,  30. 

natural,  composition  of,  32. 

Pintsch,  55. 

pressure  for  burning,  55. 

purification  of,  54. 

water,  54. 
Gas    burners    for    light    or    heat, 

48. 

Gas  lights,  Welsbach  system,  59. 
Gases,  poisonous,  21. 
Gasoline,  51. 

use  of,  32. 
Germ  flour,  175. 
Gin,  284. 
Ginger,  290. 
Globulin,  229. 
Glucose,  281. 

commercial,  200. 

composition  of,  201. 

healthfulness  of,  202. 

manufacture  of,  200,  201. 

properties  of,  202. 

sirups,  202. 

sweetness  of,  202. 

use  of,  202,  219. 
Glucose  group,  225. 
Gluten,  148,  166. 

in  flour,  173. 
Glycerin,  101. 

from  soap,  98. 
Granulated  sugar,  196. 
Grape  sugar,  200,  201. 

composition  of,  201. 

manufacture  of,  201. 
Grapes,  273. 

cultivation  of,  273. 

ripening  of,  273. 
Grease,  removal  of,  93,  94. 
Greens,  food  value  of,  208. 
Ground  air,  20. 

compared  with  atmospheric  air, 
20. 

effects  on  the  system,  21. 

germs  in  air,  21. 


INDEX 


339 


Hamburg,    Germany,  epidemic    of 

cholera  in,  76. 
Hard  water,  67. 

permanently,  67. 

temporarily,  67. 
Heat,  means  of  obtaining,  33. 
Helium,  discovery  of,  3. 
Honey,  204. 

adulteration  of,  205. 

composition  of,  205. 

food  value  of,  205. 
Household  wastes,  89. 

disposal  of,  89,  90. 
Human  body,  compounds  found  in, 
123. 

composition  of  (table),  122. 
Hydrogen,  24. 

burning  of,  24. 

peroxid,  15. 

sulfid  in  air,  14. 

Hydrogen   peroxid   as   a   disinfec- 
tant, 112. 


Iceland  moss,  210. 
Incandescent  gas  lights,  59. 
Income  necessary  for  subsistence, 

320. 

Indigo  used  in  bluing,  303. 
Infants'  foods,  174,  181. 

composition  of,  181. 
Injurious  trades,  20. 
Ink  spots,  removal  of,  95. 
Inosite,  125. 
Introduction,  xix. 
Inulin,  149. 
Invert  sugar,  215. 
Investigations  needed,  321. 
Iron  sulfate  as  disinfectant,  112. 


Jams,  adulteration  of,  219,  220. 
Jams  and  jellies,  219. 
Jellies  and  jams,  219. 


E 

Kerosene,  51. 

purification  of,  52. 
Koumiss,  244. 


Lactalbumin,  246. 
Lactometer,  243. 
Lactose,  199. 
Lamps  and  burners,  58. 
Lard,  compound,  226. 

kettle  rendered,  225. 

leaf,  225. 

neutral,  225,  254. 

prime  steamed,  225. 

refined,  225. 

scrap,  225. 

steam  rendered,  224. 

stiffening  of,  225. 
Lausen  (Switzerland),  typhoid  fever 

in,  77. 
Leaven,  167. 

use  of,  167. 

Leaves  used  as  food,  208,  209. 
Lecithin,  230. 
Leeks,  210. 
Legumes,  142. 

composition  of,  143. 

food  value  of,  143. 
Legumin,  143. 
Leguminous  foods,  cooking  of,  310. 

digestibility  of,  143. 
Lemon,  extract  of,  221,  222. 
Lentils,  142,  143. 
Lettuce,  149. 
Levulose,  204. 
Lichens,.  210. 
Light,  46. 

candle  flame,  47. 

early  sources  of,  48. 

source  of,  46. 

Light-producing  substances,  46. 
Light,  ideal,  60. 
Lighting,  46. 

common  methods  of,  46. 
Liqueurs  and  cordials,  272,  285,  286. 
Liquors,  distilled,  272,  283. 

fermented,  272. 

malt,  272. 


340 


INDEX 


Macaroni,  183. 

composition  of,  184. 

food  value  of,  184. 
Mace,  290. 
Maize,  134. 

Malt,  manufacture  of,  280. 
Malt  liquors,  2S1. 

analyses  of,  281. 
Maltose,  199,  280. 

hydrolysis  of,  199. 
Mantles,  composition  of,  59. 

life  of,  59. 
Maple  sugar,  192. 

adulteration  of,  193. 
Mashing,  280. 
Masse  cuite,  190,  195. 
Mate,  261,  263. 
Meat,  boiling,  233. 

cooking  of,  232,  233,  237. 

diseases,  236. 

effect  of  cooking  on,  232. 

food  value  of,  231,  235. 

lean,  231. 

roasting,  233. 

stewing,  234. 

structure  of,  231. 

varieties  of,  235. 

water  in,  234. 
Mercuric  chlorid  as  a  disinfectant, 

115. 

Messina,  epidemic  of  cholera,  75. 
Metals,  cleaning  of,  96. 
Milk,  242. 

adulteration  of,  249. 

albumin  in,  246. 

ash  of,  247. 

borax  in,  250. 

casein  in,  245,  246. 

changes  produced,  247. 

condensed,  248. 

dried,  249. 

evaporated,  248. 

fat  in,  243,  244. 

fore,  244. 

formaldehyde  in,  250,  302. 

from  different  anim^la,  242. 


Milk,  modified,  249. 

pasteurized,  248. 

proteids  of,  246. 

souring  of,  246. 

specific  gravity  of,  243. 

sterilized,  247. 

strippings,  244. 

total  solids  in,  244. 
Milk  sugar,  199,  246. 

manufacture  of,  246. 

properties  of,  199. 
Milwaukee  sewage  system,  86. 
Mineral  water,  64. 
Modified  milk,  249. 
Molasses,  194. 
Moss,  Carrageen,  210. 

Iceland,  210. 

Irish,  210. 
Mucin,  230. 
Muscovado  sugar,  189. 
Mushrooms,  210. 

poisonous,  211. 
Must  of  wine,  274. 
Mustard,  adulteration  of,  291. 

black,  290. 

white,  290. 
Mutton,  235. 
Myosin,  229,  231,  291. 


N 


Natural  gas,  32. 
Nitric  acid  in  air,  14. 
Nitrites  and  nitrates,  71. 

significance  of,  71. 
Nitrites  in  water,  70. 
Nitrogen,  properties  of,  6. 
Nitrogenous  foods,  228. 

classification  of,  229. 

use  of,  228. 

Non-alcoholic  beverages,  compari- 
son of,  269. 

per  capita  consumption,  257. 

use  of,  270. 
Nuclein,  230. 
Nutmegs,  290. 
Nuts,  food  value  of,  226. 

analyses  of,  226. 


INDEX 


341 


Oatmeal,  analyses  of,  135. 

food  value  of,  136. 
Oats,  135. 

Offensive  gases,  121. 
Oil,  cottonseed,  224. 

petroleum,  51. 
Oil  of  cocoanut,  224. 
Oils,  edible,  223. 

fire  test  of,  52. 

flash  point,  52. 
Oleomargarin,  254. 

manufacture  of,  254. 

production  of,  255. 

tax  on,  255. 

tests  for,  256. 

Oleo-oil,  manufacture  of,  254,  255. 
Onions,  210. 

Organic  matter  in  water,  69. 
Oven,  heat  of,  171. 
Oxidation  of  water,  79. 
Oxygen,  properties  of,  6. 
Oysters,  236. 
Ozone,  constitution  of,  15. 

discovery  of,  15. 

occurrence  of,  15. 

test  for,  15. 


Paint,  solvents  for,  93,  95. 
Paraffin,  50,  62. 
Paraguay  tea,  261. 
Parasites  in  meat,  237. 
Parsnips,  207. 
Pasteurized  milk,  248. 
Pea  sausage,  144. 
Peanuts,  227. 
Peas,  142,  143. 

green,  144. 
Peat,  27. 

abundance  of,  27. 

source  of,  27. 
Pectin,  215. 
Pectose,  125,  215. 
Peotous  bodies,  215. 
Pepper,  289. 
Pepsin,  231. 


Peptone,  229. 

Perry,  279. 

Petroleum  distillates,  51. 

Phosphate  powders,  composition  of, 

158,  160,  161. 
Physiological  action  of  alcohol,  286, 

289. 
Pie  plant,  209. 
Pintsch  gas,  55. 
Plantain,  144. 
Plastering  of  wine,  277. 
Plymouth,  Pennsylvania,  epidemic 

of  typhoid  fever,  76. 
Polishing  materials,  92,  93. 
Potassium  permanganate,  112. 
Potatoes,  138. 

analysis  of,  139. 

food  value  of,  139,  140. 

introduction  of,  138,  139. 

structure  of,  140. 

sweet,  140. 

Predigested  foods,  180,  182. 
Preface,  v. 

Preservation    of     food,    297,    298, 
299. 

history  of,  297. 

Preserved  food,  metals  in,  300. 
Preservatives,  219. 

effects  on  the  system,  301,  302, 

303. 
Preservatives  in  foods,  301. 

in  common  use,  303. 
Process  butter,  detection  of,  256. 
Proteids,  229. 
Proteoses,  229. 
Prussian  blue,  104. 
Ptyalin,.  action  of,  199. 
Purification  of  water  supplies,  79. 


Quicklime  for  disinfection,  110. 

R 

Radiation,  direct,  33. 
Radiation,  indirect,  35. 

use  of  steam,  36, 

Ramsay  and  Rayleigh,  discoveries 
of,  2. 


342 


INDEX 


Ration,  ideal  (table),  319. 
Reduction  to  destroy  refuse,  90,  91. 
Refining  sugar,  194,  195. 
Rennet,  246. 
Respiration,  39. 

air  needed  for,  41. 
Rhubarb,  209. 
Rice,  137. 

composition  of,  138. 

food  value  of,  138. 

preparation  of,  137. 
Richard's  ideal  ration,  319. 
River  water,  62. 
Roots  used  as  food,  207. 
Rum,  284. 
Rye,  136. 

composition  of,  137. 
Rye  flour,  136. 


S 


Saccharin,  186,  219. 

in  foods,  304. 

tests  for,  305. 
Sago,  141. 
Sake,  282. 
Salep,  142. 
Salt,  295. 

composition  of,  295. 

production  of,  295. 
Salt-rising  process,  168. 
Sanitary  analysis  of  water,  69. 
Saponification,  97,  98. 
Sauerkraut,  209. 
Scurvy,  237. 
Separator,  use  of,  244. 
Septic  tank,  88. 
Sewage,  composition  of,  84,  85. 

definition  of,  83,  84. 

disposal  of,  by  dilution,  95,  96. 

precipitation  of,  88. 

purification  of,  85. 
Sewage  disposal,  84. 

by  chemical  precipitation,  88. 

by  intermittent  nitration,  87. 

by  irrigation,  87. 

by  septic  tank,  88. 
Shale  oil,  50. 
Silver,  cleaning  of,  96. 


Sirup,  maple,  adulteration  of,  192. 
Sirups,  fruit,  221. 
Snow,  use  of,  in  baking,  155. 
Soap,  92. 

castile,  99. 

Chevreul's  researches,  101. 

cocoanut  oil,  99. 

economy  in  use  of,  101. 

glycerin  from,  101. 

hard,  101. 

lye,  100. 

manufacture  of,  98. 

mottled,  98. 

sand,  100. 

soft,  100. 

theory  of  action,  101. 

toilet,  100. 

transparent,  100. 

yellow,  99. 

Soap-making  materials,  91. 
Soap  solution,  68. 
Sodium    bicarbonate,    use     of,     in 

baking,  155,  157. 
Sodium  sulfite  in  fruits,  304. 
Softening    of    water    by    Clarke's 

process,  82. 
Sorghum  sugar,  193. 
Sour  milk,  246. 

use  of,  in  baking,  157. 
Soy  beans,  142. 
Spaghetti,  183. 
Spices,  288. 

Stalks,  used  as  food,  208,  209. 
Standard  dietaries,  217,  218. 
Starch,  128. 

adulteration  of,  142. 

chemical  properties  of,  150. 

detection  of  source  of,  150. 

hydrolysis  of,  152. 

in  cereals,  128. 

in  fruits,  129,  214. 

in  legumes,  129. 

in  nuts,  129. 

in  roots,  129. 

in  wheat,  129. 

making  from  wheat,  147. 

methods  for  making,  146,  147. 

physical  properties,  149,  150. 

sources  of,  128. 


INDEX 


343 


Starchy  foods,  cooking  of,  308. 

Steam  for  heating,  36. 

Steam  heat  for  disinfection,  113. 

Steamer,  use  of,  311. 

Sterilized  milk,  247. 

Stoves,  precautions  in  use  of,  35. 

use  of,  34. 

ventilation  with,  34. 
Subsistence,  income  used,  320. 
Sucrose,  187. 
Sugar,  maple,  192. 

adulteration  of,  193. 

manufacture  of,  193. 

sorghum,  193. 
Sugar,  powdered,  196. 

production  of,  190. 

properties  of,  197. 

refining,  194,  195. 

spots,  removal  of,  95. 

sources  of,  187. 

triple  effect  evaporators,  189. 

use  of  boneblack,  189. 
Sugar  beets,  190. 
Sugar  cane,  cultivation  of,  187,  188. 

making  sugar  from,  188. 
Sugar  making,  188,  189. 
Sugars,  analyses  of,  198. 

adulteration  of,  194,  197. 

boiling,  189. 

classification  of,  185,  186. 

consumption  of,  186. 

cut,  197. 

filtration  of,  195. 

food  value  of,  198,  199. 

granulated,  196. 

history  of,  185. 

in  fruits,  215. 

in  fruits  (table),  293. 

inversion  of,  190,  193,  204. 
Sunlight  as  a  disinfectant,  109. 
Sweet  potatoes,  140. 

composition  of,  140. 
Synthetic  foods,  121. 


Table  of  contents,  vii. 
Tallow,  49. 
Tannin,  in  tea,  261. 


Tannin,  in  coffee,  264. 
Tapioca,  141. 

preparation  of,  141. 
Tartrate  baking  powders,  159. 
Taste,  delicacy  of  the  sense,  118. 
Taste  and  smell,  118. 

use  of,  118. 
Tea,  258. 

action  on  the  system,  259. 

adulteration  of,  259. 

amount  imported,  257. 

analyses  of,  260. 

black  vs.  green,  258. 

coffee  leaf,  262. 

cultivation  of,  258. 

green,  258. 

history  of  cultivation,  258. 

Indian,  259. 

Japan,  258. 

lye,  260. 

Paraguay,  261. 

preparation,  258. 

preparation  of  beverage,  260. 

spurious,  259. 

tannin,  261. 

thein,  261. 
Tees  Valley,   epidemic   of   typhoid 

fever  in,  75. 
Theobromin,  267. 
Toadstools,  210,  211. 
Tomatoes,  210. 

canned,  298. 
Touf  lea  Mots,  142. 
Trades,  injurious,  20. 
Truffles,  211. 
Turnips,  207. 

Typhoid    fever    epidemic  in  Tees 
Valley,  75. 

in  Lausen,  Switzerland,  77. 
Tyrotoxicon  in  cheese,  252. 

U 

Ultramarine,  104. 
use  of,  196. 

V 

Vacuum  pan,  189,  195,  201. 
Vanilla,  extract  of,  221. 
Veal,  235. 


INDEX 


Ventilation,  33,  38. 

by  natural  or  forced  draft,  42. 

conditions  necessary,  42. 

exhaust  fans,  43. 

importance  of,  38,  39. 

open  grates,  44. 

special  devices,  44. 
Vermicelli,  183. 
Vinegar,  291. 

acid  of,  293. 

caramel  in,  294. 

cider,  293. 

fermentation  in,  292. 

imitation,  293. 

materials  used,  292. 

quick  process,  292,  293. 

wine,  293. 
Voit,  experiments  by,  315. 

W 

Wall  paper,  arsenic  in,  19. 
Washing  soda,  101. 

use  of,  102,  103. 
Waste  of  food,  320,  321. 
Water,  61. 

analyses  of  city  supplies,  72. 

chlorin  in,  71. 

cistern,  61. 

drinking  and  disease,  74. 

effect  of  freezing  on,  73. 

filtration  and  softening,  80. 

filtration  by  sand,  80. 

free  ammonia  in,  70. 

Hamburg    (Germany),   analyses 
of,  77. 

hard,  67. 

in  air,  6,  7. 

in  meat,  234. 

lake,  62. 

mineral,  64. 

mineral  substances  in,  64. 

mechanical  filtration,  81. 

natural,  61. 

nitrates  in,  61. 

nitrites  in,  70. 

organic  matter  in,  69. 

oxidation  of,  79. 

polluted  by  sewage,  74. 


Water,  rain,  62. 

sanitary  analysis  of,  69. 

softening,  Clarke's  process,  82. 

spring,  62. 

storage,  63. 

turbid,  74. 

well,  63. 
Water,  hot,  for  heating,  37. 

advantage  over  steam,  37. 
Water  supplies,  79. 

purification  of,  79. 

purification  by  dilution,  79. 
Waters,  hard,  67. 

disadvantages  of,  68. 
Well  water,  63. 

artesian,  63,  64. 

impurities  in,  63. 

wells,  domestic,  dangers  of,  63. 
Welsbach  lights,  59. 
Wheat,  130. 

proteids  of,  130. 

Russian,  131. 

starch  in,  147. 

structure  of  grain,  130. 

varieties  of,  130. 
Wheat  flour,  131. 

analyses  of,  131,  132,  133. 

patent,  134. 

value  of,  132. 
Whey,  246. 

use  of,  199. 
Whisky,  284. 
White  bread,  175. 
Wine,  273. 

adulteration  of,  277. 

aging  of,  274. 

analyses  of,  275,  276. 

chaptalising  of,  277. 

classification  of,  276. 

manufacture  of,  274. 

old,  275. 

plastering,  277. 

still,  276. 

tannin  in,  275. 
Wood,  ash  of,  26. 

drying  of,  26. 

seasoning  of,  26. 

water  in,  25. 
Wood  aa  fuel,  20. 


INDEX 


345 


Wort,  280. 

Wounds,  lacerated,  care  of,  115. 


Xanthin,  231. 
Xyloiden,  153. 


Yeast,  165,  280. 
cakes,  167. 


Yeast,  compressed,  166. 
cultivation  of,  166. 
domestic,  167. 
history  of  use,  166. 
in  beer,  280,  281. 
use  of,  165. 

Z 

Zinc  chlorid  for  disinfection,  112. 


"""THE  following  pages  contain  advertisements  of  a 
few  of  the  Macmillan  books  on  kindred  subjects 


MUNICIPAL   ENGINEERING  AND 
SANITATION 

By  V.  N.  BAKER,  PIiB. 

Associate  Editor  of  Engineering  Newt 

umo.    Half  Leather.    $1.25,  net 

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nected with  the  administration  of  various  public  works  having  an  engineering 
or  sanitation  side.  That  which  most  impresses  the  reader  is  the  wide  range 
of  observation  from  which  Mr.  Baker  speaks.  .  .  .  The  reports  of  foreign 
engineers  upon  experiments  abroad  are  also  frequently  used,  but  the  work 
is  better  for  American  readers  because  American  experience  is  kept  constantly 
in  the  foreground." —  The  Outlook. 


THE   MACMILLAN   COMPANY 

64-66  FIFTH  AVENUE,   NEW  YORK 


PRINCIPLES  OF  SANITARY  SCIENCE  AND 
THE  PUBLIC  HEALTH 

WITH    SPECIAL    REFERENCE    TO    THE    CAUSATION 
AND  PREVENTION  OF  INFECTIOUS  DISEASES 

By  WILLIAM  T.  SEDGWICK,  Ph.D. 

Professor  of  Biology  and  Lecturer  on  Sanitary  Science  and  the  Public  Health  in 
the  Massachusetts  Institute  of  Technology 

Cloth  8vo  $3.00,  net 

"The  book  is  a  most  excellent  one.  No  one  in  this  country  is  better  fitted 
to  write  it,  and  Professor  Sedgwick  has  succeeded  exceptionally  well  in  pre- 
senting the  subject  in  a  comprehensive  and  intelligible  style.  The  book  will 
be  extremely  useful,  and  a  debt  of  obligation  is  due  to  you  and  Professor 
Sedgwick  for  the  work."  —  H.  W.  CONN,  Professor  of  Biology,  Wesleyan 
University. 

"  I  regard  it  as  a  valuable  addition  to  the  literature  of  Sanitary  Science,  and 
shall  take  great  pleasure  in  recommending  it  to  my  class  next  year  among  the 
books  for  collateral  reading."  —  DR.  CHARLES  HARRINGTON,  Harvard  Medi- 
cal School. 

"The  work  is  admirable,  as  might  naturally  be  expected,  and  I  am  sure  it 
will  do  much  to  advance  the  cause  of  Sanitary  Science  in  this  country."  — 
H.  L.  RUSSELL,  Wisconsin  State  Board  of  Health. 

"The  name  of  the  author  is  a  guarantee  of  the  excellence  of  the  book.  I 
am  much  pleased  with  the  arrangement  and  interesting  presentation  of  the 
subject-matter."  —  WILLIAM  H.  WELCH,  M.D.,  President  Rockefeller  Insti- 
tute for  Medical  Research. 


THE   MACMILLAN   COMPANY 

64-66  FIFTH  AVENUE,   NEW  YORK 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


Form  L9-10m-3,'48(A7920)444 


THE  LIBRARY 
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UCLA-Chemistry  Library 

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